Supercritical water (SCW) as a reaction medium is especially promising for the production of renewable chemicals from biomass. Stability issues of catalyst support materials in SCW are a major setback for these reactions and hinder the further development and industrial exploitation of this technique. The development of stable catalytic support materials for reactions in SCW is, therefore, of great importance. Carbon nanotubes (CNTs) are widely recognized for their significant physical and chemical stability, high heat conductivity, and open structure. These properties have already been explored for different applications. We show that CNTs are a promising stable catalyst support material for reactions in SCW. As an illustration of the applicability of CNTs in SCW, we demonstrate the efficiency of Pt-CNTs as catalysts for the production of hydrogen by reforming of ethylene glycol and acetic acid in SCW.