Pagination For Category ??

Ok on my blog home page (index.php) in using this for pagination..

<?php $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
      query_posts("posts_per_page=9&paged=$paged"); ?>

<?php if (have_posts()) : ?>
<?php $post = $posts[0]; ?>
<?php while (have_posts()) : the_post();
?>

..whick works great. But I dont have any pagination on my Categories pages (categroy.php) I would like to have it work similar to the index page and have tried pasting in the above code but it returns all posts not just the category posts ??

How can i modift the above pagination so for each category it only returns the category posts??

I’ve tried adding..
query_posts("cat=4&posts_per_page=9&paged=$paged"); ?>

cat=4 above for example but the my other categories only return this too…

Help, i dont really understand this stuff !!