  Large column densities, derived from X-ray studies, are typically measured
towards AGN hosting water masers, especially when the H2O emission is
associated with the nuclear accretion disk. In addition, possible correlations
between the intrinsic X-ray luminosity and the characteristics of the H2O maser
emission have been put forward that, however, require confirmation. We have
performed high-sensitivity XMM-Newton observations of a sample of five H2O
maser sources confidently detected in our ongoing survey with the Swift
satellite of all known water masers in AGN, in order to obtain detailed X-ray
information of these promising targets and to set up a systematic detailed
study of the X-ray/H2O-maser relation in AGN. For three galaxies, NGC 613,
VIIZw73, and IRAS 16288+3929, the amount of intrinsic absorption has been
estimated, indicating column densities of 4-6x10^23 cm^-2. For UGC 3789 and NGC
6264 (the two confirmed disk-maser galaxies in our sample), column densities in
excess of 1x10^24 cm^-2 are inferred from the large EW of the Fe Kalpha line.
By adding our results to those obtained in past similar studies, we find that
the percentage of water masers sources that host highly-obscured (NH>10^23
cm^-2) and Compton-thick AGN is 96% (45/47) and 57% (27/47), respectively. In
addition, 86%, 18/21, of disk maser galaxies host Compton-thick AGN. The
correlation between the galaxies' bolometric luminosity and accretion disk
radius, suggested in previous works, is also confirmed.
