Polycrystalline CdS nanowires have been synthesized by sulfurizing metal Cd nanowires deposited electrochemically within the nanochannels of porous anodic alumina (PAA) templates. Photoluminescence (PL) investigation shows that the CdS nanowires have an intensive and broad PL emission band peaked around 435nm. The investigation results suggest that localized defects and excess S atoms existing in the CdS nanowires are responsible for this blue luminescence.