hi.
i need to show some specific related items in item page.
is it possible to get the into extra field the list of the items - and show in the item page the only selected items?

Hi. No this cannot be done. The proper way to do this is to use a module or a plugin, not extra fields.

thanks.
wich plugin will do the job?

I am not aware of one, nor have I used one (I use K2's default related items).
There are several extensions however posted at the JED extensions.joomla.org/