Porous CdS nanowire (NW) arrays have been synthesized by self-assemble of CdS nanoparticles (NPs) inside Sn2+/ Pd2+ -activated nanochannels of anodic aluminum oxide (AAO) template. XRD analysis indicates that the as-synthesized CdS NWs are hexagonal crystalline. TEM and SEM observations reveal that the CdS NWs are porous and consists of self-assembled CdS NPs.