diff --git a/src/timeline/component/GroupSet.js b/src/timeline/component/GroupSet.js
index c3b612a9..1e94fa3c 100644
--- a/src/timeline/component/GroupSet.js
+++ b/src/timeline/component/GroupSet.js
@@ -257,7 +257,6 @@ GroupSet.prototype.repaint = function repaint() {
   });
 
   // reposition the labels and calculate the maximum label width
-  // TODO: labels are not displayed correctly when orientation=='top'
   var maxWidth = 0;
   for (id in groups) {
     if (groups.hasOwnProperty(id)) {
@@ -327,7 +326,7 @@ GroupSet.prototype.hide = function hide() {
   // hide labelset
   this.labelPanel.removeChild(this.labelSet);
 
-  // TODO: replace the following with a panel holding all itemsets, do not hide groups individually
+  // hide each of the groups
   for (var groupId in this.groups) {
     if (this.groups.hasOwnProperty(groupId)) {
       this.groups[groupId].hide();
@@ -345,7 +344,7 @@ GroupSet.prototype.show = function show() {
     this.labelPanel.removeChild(this.labelSet);
   }
 
-  // TODO: replace the following with a panel holding all itemsets, do not show groups individually
+  // show each of the groups
   for (var groupId in this.groups) {
     if (this.groups.hasOwnProperty(groupId)) {
       this.groups[groupId].show();
@@ -378,18 +377,12 @@ GroupSet.prototype._onAdd = function _onAdd(ids) {
         height: null
       });
 
-      // TODO: do not recreate the group with every update
-
       group = new Group(me, me.labelSet, me.backgroundPanel, me.axisPanel, id, groupOptions);
       group.on('change', me.emit.bind(me, 'change')); // propagate change event
       group.setRange(me.range);
       group.setItems(me.itemsData); // attach items data
       me.groups[id] = group;
       group.parent = me;
-
-      // Note: it is important to add the binding after group.setItems
-      // is executed, because that will start an infinite loop
-      // as this call will already trigger a repaint
     }
 
     // update group data
diff --git a/src/timeline/component/ItemSet.js b/src/timeline/component/ItemSet.js
index 6ac1c0a2..77233381 100644
--- a/src/timeline/component/ItemSet.js
+++ b/src/timeline/component/ItemSet.js
@@ -10,7 +10,6 @@
  * @constructor ItemSet
  * @extends Panel
  */
-// TODO: improve performance by replacing all Array.forEach with a for loop
 function ItemSet(backgroundPanel, axisPanel, options) {
   this.id = util.randomUUID();
 
@@ -54,8 +53,6 @@ function ItemSet(backgroundPanel, axisPanel, options) {
 
   this.touchParams = {}; // stores properties while dragging
 
-  // TODO: ItemSet should also attach event listeners for rangechange and rangechanged, like timeaxis
-
   // create the HTML DOM
   this._create();
 }
@@ -97,7 +94,7 @@ ItemSet.prototype._create = function _create(){
   this.axisPanel.frame.appendChild(axis);
 
   // attach event listeners
-  // TODO: use event listeners from the rootpanel to improve performance
+  // TODO: use event listeners from the rootpanel to improve performance?
   this.hammer = Hammer(frame, {
     prevent_default: true
   });
@@ -330,7 +327,7 @@ ItemSet.prototype.repaint = function repaint() {
   }
 
   // reposition visible items vertically
-  //this.stack.order(this.visibleItems); // TODO: solve ordering issue
+  //this.stack.order(this.visibleItems); // TODO: improve ordering
   var force = this.stackDirty || zoomed; // force re-stacking of all items if true
   this.stack.stack(this.visibleItems, force);
   this.stackDirty = false;
@@ -500,7 +497,6 @@ ItemSet.prototype._onUpdate = function _onUpdate(ids) {
 
     var constructor = ItemSet.types[type];
 
-    // TODO: how to handle items with invalid data? hide them and give a warning? or throw an error?
     if (item) {
       // update item
       if (!constructor || !(item instanceof constructor)) {
@@ -582,10 +578,6 @@ ItemSet.prototype._order = function _order() {
   // reorder the items
   this.stack.orderByStart(this.orderedItems.byStart);
   this.stack.orderByEnd(this.orderedItems.byEnd);
-
-  // TODO: cleanup
-  //console.log('byStart', this.orderedItems.byStart.map(function (item) {return item.id}))
-  //console.log('byEnd', this.orderedItems.byEnd.map(function (item) {return item.id}))
 };
 
 /**
diff --git a/src/timeline/component/Panel.js b/src/timeline/component/Panel.js
index 84d70e7b..eb4264c5 100644
--- a/src/timeline/component/Panel.js
+++ b/src/timeline/component/Panel.js
@@ -11,7 +11,7 @@
  */
 function Panel(options) {
   this.id = util.randomUUID();
-  this.parent = null; // TODO: remove parent?
+  this.parent = null;
   this.childs = [];
 
   this.options = options || {};