Some principal problems arising in the stage of design of photodetection system used for lidar studies are treated in the paper. Results of experimental investigation of the characteristics of photomultiplier tubes operating in the photon counting mode are discussed. Recommendations for use of the photomultipliers in special–purpose lidars have been given. The problems arising in the stage of design of amplitude discriminators and single–electron pulse counters are treated. Specifications of the developed photon counting systems are presented.