A laser pulse propagating through dense clouds suffers from spatial and temporal distortion caused by multiple scattering of light. Both distortions are function of the optical depth, the particle size of the aerosols and the cloud distance relative to the target and receiver. In order to study the effects of all theses parameters, 3-D Monte-Carlo (MC) simulations were performed. The Monte Carlo developed for this purpose has the unique capability to produce both 2D and 3D images of the scenes. For the 2D images we calculated the MTF using the Fourier transform of the system PSF. For the 3D images gratings with rectangular grooves of various frequencies and height were used and the concept of contrast applied as for the calculation of MTF for 2 D images. We found that 3D temporal distortion effects are significantly reduced when the reconnaissance algorithm is base on the shape of the raising pulse.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.