Photoremovable protecting groups (PPG) are of current interest because of their numerous practical applications, especially in organic synthesis and biological sciences. This review describes the most important families of PPGs: the 2-nitrobenzyl, 2-nitroanilino, phenacyl, phenoxy, azidoaryl, and sulfonic ester groups. It also comments on mechanisms of their photo-induced deprotection in some cases. Chemical and quantum yields of the deprotection are provided.