  We cross-correlate the recent CMB WMAP 1 year data with the diffuse soft
X-ray background map of ROSAT. We look for common signatures due to galaxy
clusters (SZ effect in CMB, bremsstrahlung in X-rays) by cross-correlating the
two maps in real and in Fourier space. We do not find any significant
correlation and we explore the different reasons for this lack of correlation.
The most likely candidates are the possibility that we live in a low $\sigma
_8$ universe ($\sigma_8 < 0.9$) and/or systematic effects in the data
especially in the diffuse X-ray maps which may suffer from significant cluster
signal subtraction during the point source removal process.
