The Sunyaev--Zel'dovich (SZ) effect is a powerful new tool for finding clusters at high redshift, particularly in combination with their X-ray properties. In this presentation we quantify the expected scaling relations between these properties using high-resolution hydrodynamical N-body simulations of large scale structure with various models for heating and cooling of the cluster gas.

  In conjunction with simulated maps, these relations are of great importance to understand selection effects on detected objects and to determine the amplitude of measurement errors under different observational strategies for future SZ and cosmic microwave background (CMB) experiments, such as AMI, AMiBA and PLANCK.