Topically applicable cosmetic/dermatological sunscreen compositions well suited for the UV-photoprotection of human skin and/or hair against the damaging effects of UV-A and UV-B irradiation, particularly solar radiation, comprise (i) a UV-photoprotecting effective amount of at least one solubilized organolipophilic silicon compound, whether solid silane or organopolysiloxane, bearing a benzotriazole function substituent and (ii) an amount of at least one cinnamic acid sunscreen compound and/or at least one salicylic acid sunscreen compound effective to (substantially) dissolve said at least one organolipophilic silicon compound.