Definition

		<xul:menulist>
			<xul:menupopup>
				<xul:menuitem label="Chapter 1" value="Value 1" selected="true"/>
				<xul:menuitem label="Chapter 2" value="Value 2"/>
				<xul:menuitem label="Chapter 3" value="Value 3"/>
			</xul:menupopup>
		</xul:menulist>

Code
			//alert("Unselecting");
			this.mChapterList.selectedIndex = -1;
			
			//alert("Emptying");
			this.mChapterList.removeAllItems();
			this.mChapterList.appendItem("Label 0", "Value 0");
			this.mChapterList.appendItem("Label 1", "Value 1");
			this.mChapterList.appendItem("Label 2", "Value 2");

			var nodes = this.mChapterList.getElementsByTagName("menuitem"); 
			alert("Just a test "+nodes[0].label);
			alert("Another test "+nodes[0].label);