Studying clusters with Planck

We use mock Sunyaev-Zeldovich effect 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. For the simplest methods, the catalogs are not complete, even for relatively high mass thresholds, but the all-sky nature of the mission ensures a large sample of massive, high-z clusters that 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.