If you try to add permissions to a user by using PeoplePicker control, sometimes users won't appear in that dialog box. To solve this first you need to check what is the directory path for that webapplication then to set it to include all users in your domain. You can do this only by using stsadm utility. To use stsadm you need to open cmd and change the working directory to "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\BIN" To check the current path: stsadm -o getsiteuseraccountdirectorypath -url http://webapp To change this to include all users in your domain use this: stsadm -o setsiteuseraccountdirectorypath -path "" -url http://webapp