arba

Solved it already in this way:

<?php
 if ( is_category() ) {

	$this_cat = get_category($cat);
        $sub_cats = get_categories('child_of='.$this_cat->term_id.'&hide_empty=false&orderby=name');

	if ( !empty( $sub_cats ) ) {
		foreach( $sub_cats as $sub ){			

        if ( $sub->category_parent == $this_cat->term_id) {

			$link = get_category_link( $sub->term_id );
			$link_title = $sub->name;

			echo '<div class="post">';
			echo '<h2><a href="'.$link.'" rel="bookmark" title="Permanent Link to '.$link_title.'">'.$link_title.'</a></h2>';

			echo $sub->description;
			echo '</div>';
                        }
		}
	}
}
?>