diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/AssignedMaterialsToOrderElementController.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/AssignedMaterialsToOrderElementController.java
index 7fab34b7b..3735ad9fa 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/AssignedMaterialsToOrderElementController.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/AssignedMaterialsToOrderElementController.java
@@ -394,8 +394,50 @@ public class AssignedMaterialsToOrderElementController extends
     private void removeMaterialAssignment(MaterialAssignment materialAssignment) {
         assignedMaterialsToOrderElementModel.removeMaterialAssignment(materialAssignment);
         Util.reloadBindings(gridMaterials);
-        // Reload categoriesTree
-        categoriesTree.setModel(getMaterialCategories());
+        reloadTree(categoriesTree);
+    }
+
+    private void reloadTree(Tree tree) {
+        final Treeitem treeitem = tree.getSelectedItem();
+
+        if (treeitem != null) {
+            final MaterialCategory materialCategory = (MaterialCategory) treeitem.getValue();
+            tree.setModel(getMaterialCategories());
+            locateAndSelectMaterialCategory(tree, materialCategory);
+        } else {
+            tree.setModel(getMaterialCategories());
+            Util.reloadBindings(gridMaterials);
+        }
+    }
+
+    private boolean locateAndSelectMaterialCategory(Tree tree, MaterialCategory materialCategory) {
+        Treeitem treeitem = findTreeItemByMaterialCategory(tree.getRoot(), materialCategory);
+        if (treeitem != null) {
+            treeitem.setSelected(true);
+            return true;
+        }
+        return false;
+    }
+
+    @SuppressWarnings("unchecked")
+    private Treeitem findTreeItemByMaterialCategory(Component node, MaterialCategory materialCategory) {
+        if (node instanceof Treeitem) {
+            final Treeitem treeitem = (Treeitem) node;
+            final MaterialCategory _materialCategory = (MaterialCategory) treeitem.getValue();
+            if (_materialCategory.getId().equals(materialCategory.getId())) {
+                return treeitem;
+            }
+        }
+        for (Iterator i = node.getChildren().iterator(); i.hasNext(); ) {
+            Object obj = i.next();
+            if (obj instanceof Component) {
+                Treeitem treeitem =  findTreeItemByMaterialCategory((Component) obj, materialCategory);
+                if (treeitem != null) {
+                    return treeitem;
+                }
+            }
+        }
+        return null;
     }
 
     /**
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/AssignedMaterialsToOrderElementModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/AssignedMaterialsToOrderElementModel.java
index 88a6a270d..dff40379a 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/AssignedMaterialsToOrderElementModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/AssignedMaterialsToOrderElementModel.java
@@ -191,7 +191,7 @@ public class AssignedMaterialsToOrderElementModel implements
                     .getMaterialAssignments()) {
                 final Material material = materialAssigment.getMaterial();
                 if (materialCategory == null
-                        || materialCategory.equals(material.getCategory())) {
+                        || materialCategory.getId().equals(material.getCategory().getId())) {
                     result.add(materialAssigment);
                 }
             }
@@ -231,8 +231,24 @@ public class AssignedMaterialsToOrderElementModel implements
     }
 
     @Override
+    @Transactional(readOnly = true)
     public void removeMaterialAssignment(MaterialAssignment materialAssignment) {
         orderElement.removeMaterialAssignment(materialAssignment);
+        // Remove material category from materialCategories tree
+        final MaterialCategory materialCategory = materialAssignment.getMaterial().getCategory();
+        removeCategory(materialCategories, materialCategory);
+    }
+
+    private void removeCategory(
+            MutableTreeModel<MaterialCategory> materialCategories,
+            MaterialCategory materialCategory) {
+
+        categoryDAO.reattach(materialCategory);
+        final boolean canDelete = materialCategory.getSubcategories().isEmpty() &&  getAssignedMaterials(materialCategory).isEmpty();
+        if (canDelete) {
+            materialCategories.remove(materialCategory);
+            removeCategory(materialCategories, materialCategory.getParent());
+        }
     }
 
     @Override