The determination of volatile organic compounds (VOCs) in exhaled air and stomach tissue emission for the detection of cancer has been investigated. Solid phase microextraction (SPME) was used for sample preconcentration. The method presented in this paper showed satisfactory precision (RSD below 11%), linearity in the range of 2.8-136 ppb and limit of detection ranging from 0.6 to 2.1 ppb. The breath and emission from cancer tissue were collected from three patients with stomach cancer. Acetone, carbon disulfide, 2-propanol, ethyl alcohol and ethyl acetate were identified in breath and tissue samples. These compounds have been assumed as endogenous. Acetone ratio (AR) was calculated for carbon disulfide, 2-propanol and n-butane. The AR for carbon disulfide was found to be higher for normal tissue (20.64-44.95) than for emission from cancer tissue (2.01-18.20). A limitation of this study is that only a few clinical samples were investigated. These results should be evaluated as preliminary because of the small number of patients examined.