The preparation of cadmium sulfide nanoparticles that have a moderate pore size is reported. This preparation method involves a hydrothermal process that produces a precursor mixture and a following acid treatment of the precursor to get the porous material. The majority of the particles have a pore size close to 20 nm, which complements and fills in the gap between the existing cadmium sulfide materials, which usually have a pore size either less than 10 nm or are well above 100 nm. (c) 2007 Elsevier Inc. All rights reserved.