The Lidar technique is an efficient tool for continuous monitoring of clouds and aerosols, with high temporal and spatial resolution. Lidar systems can provide long-term accurate information on cloud top and base heights and their optical depth. The spatial distribution of clouds and the diurnal variation of cloud properties are important parameters in many operational and research applications (i.e. radiative transfer modeling, energy balance, meteorology, etc.). In this paper, we present the application of a compact mobile lidar system in monitoring of cloud properties, over Athens, Greece. Preliminary lidar measurements were performed during summer- autumn 1994, focusing on the study of short-time variability of spectral cloud properties at two wavelengths (355 nm and 532 nm), using a compact Nd:YAG laser. The Lidar dataset acquired is analyzed during selected cases and conclusions are drawn.