Аннотация:Although the frequency position of the non-coupled state in coherent population trapping does not depend on light intensities, this is not true for the experimentally observed dark resonance minimum. For precision applications, this shift constitutes a major systematic effect. We have measured the light shift in an atomic celsium vapor, as a function of buffer gas pressures. The experimental data for the unbuffered vapor can be reproduced quantitatively with a simple model, taking into account the atomic velocity distribution and the excited state hyperfine structure. The buffered vapor requires a more complicated model.