// Normal dropdownlist
<?php echo $form->dropDownList($model, 'field_name', array(1=>'test1', 2=>'test2'));?>
// List data need when populating dropdown from database values
<?php echo $form->dropDownList($model,'node_types_id', CHtml::listData(NodeTypes::model()->findAll(array('order' => 'name')),'id','name'));?>