Why render funcion hide img tags? I have a simple text that contains  tags but when I try to render the field, the img tags disappear!

&lt;?php print render($content['field_with_img_tags']); ?&gt;


Why?
What type of field are you using ? If it is a body_format using a format (i.e.: Filtered HTML, Full HTML) verify the filter settings. Probably Limit allowed HTML tags is enabled and the  tag is not part of the allowed tags.

To verify / change settings, it is under admin/config/content/formats and click on configure link of your used format.