A process for producing high purity hyrogen is disclosed. Specifically, the process includes (1) partially oxidizing a gaseous hydrocarbonaceous feedstock to produce a synthesis gas mixture of carbon monoxide and hydrogen, (2) reacting the synthesis gas mixture with steam to convert the carbon monoxide into a raw gas mixture which primarily includes carbon dioxide and hydrogen, and (3) subjecting the raw gas mixture to pressure swing adsorption to purify the raw gas mixture, thereby producing high purity hydrogen and a reject gas mixture of impurities.The gaseous hydrocarbonaceous feed is specific, inasmuch as it is characterized by containing a major component which includes at least one C.sub.1 -C.sub.3 hydrocarbon and which has an average molecular weight of up to about 30.