diff --git a/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskComponent.java b/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskComponent.java
index cf8f28231..72187e556 100755
--- a/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskComponent.java
+++ b/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskComponent.java
@@ -128,11 +128,21 @@ public class TaskComponent extends Div implements AfterCompose {
         }
     };
 
-    public static TaskComponent asTaskComponent(Task task, TaskList taskList) {
+    public static TaskComponent asTaskComponent(Task task, TaskList taskList,
+            boolean isTopLevel) {
+        final TaskComponent result;
         if (task.isContainer()) {
-            return TaskContainerComponent.asTask((TaskContainer) task, taskList);
+            result = TaskContainerComponent
+                    .asTask((TaskContainer) task, taskList);
+        } else {
+            result = new TaskComponent(task);
         }
-        return new TaskComponent(task);
+        result.isTopLevel = isTopLevel;
+        return result;
+    }
+
+    public static TaskComponent asTaskComponent(Task task, TaskList taskList) {
+        return asTaskComponent(task, taskList, true);
     }
 
     public TaskComponent(Task task) {
@@ -174,6 +184,8 @@ public class TaskComponent extends Div implements AfterCompose {
 
     private List<WeakReference<DependencyAddedListener>> dependencyListeners = new LinkedList<WeakReference<DependencyAddedListener>>();
 
+    private boolean isTopLevel;
+
     private final Task task;
     private PropertyChangeListener propertiesListener;
 
@@ -344,4 +356,9 @@ public class TaskComponent extends Div implements AfterCompose {
         getDependencyList().taskRemoved(this.getTask());
         this.detach();
     }
+
+    public boolean isTopLevel() {
+        return isTopLevel;
+    }
+
 }
diff --git a/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskContainerComponent.java b/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskContainerComponent.java
index 59435695a..94ed84b9a 100644
--- a/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskContainerComponent.java
+++ b/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskContainerComponent.java
@@ -53,11 +53,14 @@ public class TaskContainerComponent extends TaskComponent implements
         taskContainer.addExpandListener(expandListener);
         this.taskList = taskList;
         for (Task task : taskContainer.getTasks()) {
-            getCurrentComponents().add(
-                    TaskComponent.asTaskComponent(task, taskList));
+            getCurrentComponents().add(createChild(task));
         }
     }
 
+    private TaskComponent createChild(Task task) {
+        return TaskComponent.asTaskComponent(task, this.taskList, false);
+    }
+
     @Override
     protected void publishDescendants(Map<Task, TaskComponent> resultAccumulated) {
         for (TaskComponent taskComponent : getCurrentComponents()) {
@@ -79,7 +82,7 @@ public class TaskContainerComponent extends TaskComponent implements
             Collection<? extends Task> newTasks) {
         List<TaskComponent> taskComponents = new ArrayList<TaskComponent>();
         for (Task task : newTasks) {
-            taskComponents.add(TaskComponent.asTaskComponent(task, taskList));
+            taskComponents.add(createChild(task));
         }
 
         if (insertionPosition == null) {
@@ -103,7 +106,8 @@ public class TaskContainerComponent extends TaskComponent implements
 
     private void addAllAt(Component previous, List<TaskComponent> toAdd) {
         for (TaskComponent subtaskComponent : toAdd) {
-            taskList.addTaskComponent(previous, subtaskComponent, true);
+            taskList.addTaskComponent(previous.getNextSibling(),
+                    subtaskComponent, true);
             previous = subtaskComponent;
         }
     }
diff --git a/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskList.java b/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskList.java
index c47c15f82..84f87f459 100644
--- a/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskList.java
+++ b/navalplanner-gantt-zk/src/main/java/org/zkoss/ganttz/TaskList.java
@@ -60,7 +60,8 @@ public class TaskList extends XulElement implements AfterCompose {
 
     public static TaskList createFor(
             CommandOnTaskContextualized<?> editTaskCommand,
-            List<Task> tasks, List<? extends CommandOnTaskContextualized<?>> commandsOnTasksContextualized) {
+            List<Task> tasks,
+            List<? extends CommandOnTaskContextualized<?>> commandsOnTasksContextualized) {
         TaskList result = new TaskList(editTaskCommand, tasks,
                 commandsOnTasksContextualized);
         return result;
@@ -84,16 +85,12 @@ public class TaskList extends XulElement implements AfterCompose {
         return result;
     }
 
-    public synchronized void addTaskComponent(Component afterThis,
+    public synchronized void addTaskComponent(Component beforeThis,
             final TaskComponent taskComponent, boolean relocate) {
-        boolean isFirst = false;
-        if (afterThis == null) {
-            insertBefore(taskComponent, getFirstTaskComponent());
-            isFirst = true;
-        } else {
-            insertBefore(taskComponent, afterThis == null ? null : afterThis
-                    .getNextSibling());
-        }
+        final boolean isFirst = getFirstTopTaskComponent() == null
+                || getFirstTopTaskComponent().equals(beforeThis);
+        insertBefore(taskComponent, beforeThis);
+
         addContextMenu(taskComponent);
         addListenerForTaskComponentEditForm(taskComponent);
         ListIterator<WeakReference<DependencyAddedListener>> iterator = listeners
@@ -126,18 +123,11 @@ public class TaskList extends XulElement implements AfterCompose {
 
     public synchronized void addTaskComponent(
             final TaskComponent taskComponent, boolean relocate) {
-        addTaskComponent(getLastTaskComponent(), taskComponent, relocate);
+        addTaskComponent(null, taskComponent, relocate);
     }
 
-    private TaskComponent getLastTaskComponent() {
-        List<TaskComponent> taskComponents = getTaskComponents();
-        if (taskComponents.isEmpty())
-            return null;
-        return taskComponents.get(taskComponents.size() - 1);
-    }
-
-    private TaskComponent getFirstTaskComponent() {
-        List<TaskComponent> taskComponents = getTaskComponents();
+    private TaskComponent getFirstTopTaskComponent() {
+        List<TaskComponent> taskComponents = getTopLevelTaskComponents();
         if (taskComponents.isEmpty())
             return null;
         return taskComponents.get(0);
@@ -149,15 +139,15 @@ public class TaskList extends XulElement implements AfterCompose {
                 addTaskComponent(TaskComponent.asTaskComponent(t, this), true);
             }
         } else if (position.isAtTop()) {
-            int afterThisPosition = position.getInsertionPosition() - 1;
-            List<TaskComponent> taskComponents = getTaskComponents();
-            TaskComponent afterThis = afterThisPosition < 0 ? null
-                    : afterThisPosition >= taskComponents.size() ? getLastTaskComponent()
-                            : getTaskComponents().get(afterThisPosition);
+            final int insertionPosition = position.getInsertionPosition();
+            List<TaskComponent> topTaskComponents = getTopLevelTaskComponents();
+            Component beforeThis = insertionPosition < topTaskComponents.size() ? topTaskComponents
+                    .get(insertionPosition)
+                    : null;
             for (Task t : newTasks) {
                 TaskComponent toAdd = TaskComponent.asTaskComponent(t, this);
-                addTaskComponent(afterThis, toAdd, true);
-                afterThis = toAdd;
+                addTaskComponent(beforeThis, toAdd, true);
+                beforeThis = toAdd.getNextSibling();
             }
         } else {
             Task mostRemoteAncestor = position.getMostRemoteAncestor();
@@ -182,8 +172,8 @@ public class TaskList extends XulElement implements AfterCompose {
         return null;
     }
 
-
-    private void addListenerForTaskComponentEditForm(final TaskComponent taskComponent) {
+    private void addListenerForTaskComponentEditForm(
+            final TaskComponent taskComponent) {
         if (editTaskCommand == null)
             return;
         taskComponent.addEventListener("onDoubleClick", new EventListener() {
@@ -222,6 +212,16 @@ public class TaskList extends XulElement implements AfterCompose {
         return getTimeTracker().getMapper();
     }
 
+    private List<TaskComponent> getTopLevelTaskComponents() {
+        List<TaskComponent> result = new ArrayList<TaskComponent>();
+        for (TaskComponent taskComponent : getTaskComponents()) {
+            if (taskComponent.isTopLevel()) {
+                result.add(taskComponent);
+            }
+        }
+        return result;
+    }
+
     private List<TaskComponent> getTaskComponents() {
         ArrayList<TaskComponent> result = new ArrayList<TaskComponent>();
         for (Object child : getChildren()) {