Simulation studies of the CERN Compact Linear Collider (CLIC) which take intoconsideration space‐charge forces and high brightness beams are ongoing. A description of how space‐charge and wakefields are included in the simulation code is given. This allows beam particles to be tracking over relatively large distances. A description of how preservation of the small transverse emittance of a high brightness single bunch in the main linac by counteracting the instabilities generated by strong wakefields over the whole length of the linac is given. Also, there is a short summary of the simulations and experiments made with the CLIC test facility bunch compressor as an expample of the space‐charge influence on the bunch length.