Nanoporous CdS nanostructures, including nanosheets and hollow nanorods, have been prepared by a two-step aqueous route, which consists of a first precipitation of nanoporous Cd(OH)2 intermediates and a subsequent S2−/OH− ion-exchange conversion of the obtained Cd(OH)2 used as template either to nanoporous CdS nanosheets with sizes up to 60 nm and an average thickness of about 9 nm or to CdS hollow nanorods with lengths up to 30 nm and outer diameters in the range 7–14 nm. The obtained CdS nanostructures containing nanopores with diameters of ∼3 nm exhibit a very large BET surface area of about 112.8 m2 g−1. A very high hydrogen yield of about 4.1 mmol h−1 under visible light irradiation (λ ≥ 420 nm), corresponding to the highest apparent quantum yield of about 60.34% measured at 420 nm so far reported, has been attained over the obtained nanoporous CdS nanostructures loaded with monodisperse 3–5 nm Pt nanocrystals, which is due to an efficient charge separation, a fast transport of the photogenerated car...