  We use mock Sunyaev-Zel'dovich effect (SZE) maps to investigate how well the
Planck mission might find and characterize clusters of galaxies. We discuss
different combinations of frequency maps and different methods for identifying
cluster candidates. The resulting catalogues are not complete even for
relatively high mass thresholds, but the full sky nature of the mission ensures
a large sample of massive, high-z clusters which will be ideal for many
studies. We make a preliminary attempt to identify the X-ray, optical and weak
lensing properties of the Planck sample.
