  We directly compare X-ray and optical techniques of cluster detection by
combining SDSS photometric data with a wide-field ($\sim 1.8$ deg$^{2}$)
XMM-{\em Newton} survey in the North Galactic Pole region. The optical cluster
detection procedure is based on merging two independent selection methods - a
smoothing+percolation technique, and a Matched Filter Algorithm. The X-ray
cluster detection is based on a wavelet-based algorithm, incorporated in the
SAS v.5.2 package. The final optical sample counts 9 candidate clusters with
richness of more than 20 galaxies, corresponding roughly to APM richness class.
Three, of our optically detected clusters are also detected in our X-ray
survey. The most probable cause of the small number of optical cluster
candidates detected in our X-ray survey is that they are relatively poor
clusters, fainter than the X-ray flux limit (for extended sources) of our
survey $f_{x}(0.3-2 {\rm keV}) \simeq 2 \times 10^{-14} erg cm^{-2} s^{-1}$.
