The chemical surface structure of Ti-decorated single-walled carbon nanotubes (SWNTs) is studied. X-ray photoelectron spectra show that Ti adatoms on the SWNT surface oxidize even under ultra-high-vacuum conditions, presenting a serious obstacle for the use of Ti-decorated SWNTs for hydrogen storage. A subsequent deposition of Li can, however, reduce the degree of Ti oxidation, "liberating" Ti atoms for the interaction with hydrogen molecules in hydrogen storage applications.