  Selection of galaxy clusters by mass is now possible due to weak
gravitational lensing effects. It is an important question then whether this
type of selection reduces the projection effects prevalent in optically
selected cluster samples. We address this question using simulated data, from
which we construct synthetic cluster catalogues both with Abell's criterion and
an aperture-mass estimator sensitive to gravitational tidal effects. The
signal-to-noise ratio of the latter allows to some degree to control the
properties of the cluster sample. For the first time, we apply the
cluster-detection algorithm proposed by Schneider to large-scale structure
simulations.
  We find that selection of clusters through weak gravitational lensing is more
reliable in terms of completeness and spurious detections. Choosing the
signal-to-noise threshold appropriately, the completeness can be increased up
to 100%, and the fraction of spurious detections can significantly be reduced
compared to Abell-selected cluster samples.
  We also investigate the accuracy of mass estimates in cluster samples
selected by both luminosity and weak-lensing effects. We find that mass
estimates from gravitational lensing, for which we employ the zeta-statistics
by Kaiser et al., are significantly more accurate than those obtained from
galaxy kinematics via the virial theorem.
