  In a recent paper [PRE 62, 4665 (2000)] (quant-ph/0203102) Manfredi and Feix
proposed an alternative definition of quantum entropy based on Wigner
phase-space distribution functions and discussed its properties. They proposed
also some simple rules to construct positive-definite Wigner functions which
are crucial in their discussion. We show, however, that the main results
obtained and their discussion are incorrect.
