Results of measurements of atmospheric aerosol performed with multiwavelength lidar are presented. An approach to retrieve profiles of aerosol particle size distribution was elaborated. It consists in direct fit of predefined distribution (usually combination of lognormal functions with a few free parameters) to the experimental signals. The approach was used for retrieving marine aerosol distributions. Studies of behavior of the particles at the cumulus cloud base were performed as well. There the assumptions based on Twomey's model of the adiabatic parcel were used to support the retrieving technique which was adopted to analyze lidar profiles (at 355, 532 and 1064 nm wavelengths) registered in the region of the base of small warm cumulus clouds. Size distribution profiles and changes of particle effective radius within the range of 0.5 - 3 μm were discussed.