Hydrogen production has been a matter of great importance in the last decades, but a renewed interest in its production processes has emerged recently driven by the spectacular advances in fuel cell technology. This review provides a comprehensive overview of the state-of-the-art on reforming technology applicable to the development of small scale reformers. It considers some general aspects on hydrogen production technologies including the current production status, the future needs, and the advantages of decentralized hydrogen production vs its centralized generation in large capacity plants. Conventional and novel technologies are presented together with the new trends in research and development activities.