How to add extra field in admin comment section

You can add it directly through your functions.php, unfortunately this is not documented very well at all. You want to hook into add_comment_meta using add_action, to look at this further refer to line 500-ish of comment.php. It looks like this function add_comment_meta($comment_id, $meta_key, $meta_value, $unique = false) { return add_metadata(‘comment’, $comment_id, $meta_key, $meta_value, $unique); }

make a dropdown custom field with ‘cities’ list in it

You can register custom taxonomy like so: <?php // Register custom taxonomy for locations function mamaduka_register_taxonomy_location() { register_taxonomy( ‘location’, array( ‘post’ ), array( ‘hierarchical’ => true, ‘label’ => ‘Locations’, ‘public’ => true, )); } add_action( ‘init’, ‘mamaduka_register_taxonomy_location’ ); ?> for more information about custom taxonomy see Codex: http://codex.wordpress.org/Function_Reference/register_taxonomy