Optical properties of short-period CdSe/ZnSe fractional monolayer (ML) superlattices (SLs) with nominal thickness of CdSe layers in the range of 0.1–2 ML have been studied, focusing on vertical carrier transport along the growth axis. Specially designed structures have been grown by molecular beam epitaxy, containing either a single SL or a SL with an enlarged ZnCdSe quantum well located far away from the region where carriers are generated by photo-excitation. Extremely efficient vertical transport is observed for a CdSe layer thickness less than 0.7 ML, confirming formation of a perfect miniband of extended states. Localized electronic levels appear in the SL with CdSe layers thicker than 0.7 ML. However, at layer thicknesses up to 1–1.5 ML the extended states dominate the light-absorption process and the transport properties of the SL.