MCAO is a very promising technique to increase the AO corrected field of view. By now, this method was mainly studied for astronomical purposes. In case of horizontal or slant path propagation, the effects of anisoplanatism and scintillation are quite stronger than for astronomy: MCAO seems specially well-suited in this context. Therefore, many authors propose to use MCAO for laser beam control. Imaging is another potential applications: we have studied the theoretical performance of MCAO for extended source observation. We will present the results of this study.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.