How to change the size of the avatar in Drupal 7?
You should use theme_image_style instead.

**Update:

Example setting width/height attributes by hand (until it's resolved in Drupal core):

global $user;
$user = user_load($user-&gt;uid);
print theme('image_style', array( 'path' =&gt;  $user-&gt;picture-&gt;uri, 'style_name' =&gt; 'thumbnail', 'width' =&gt; '150', 'height' =&gt; '162'));


Remember to change your image style 'thumbnail' in this case to your desired width/height. Now that I think about it you don't necessarily need to use theme_image_style, you could just edit the image style thumbnail presets and get the desired results. If you want width/height HTML attributes, use the example above.