A global and seasonal distribution of cirrus clouds is presented herein on the basis of measurements made by the lidar aboard the Earth-orbiting Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite launched in April 2006. The latitude-longitude and vertical distributions of occurrence frequency of cirrus clouds measured by CALIPSO from June 2006 to June 2007 are presented. The investigation of top-layer cirrus clouds shows maximum-occurrence frequency of up to 70% near the tropics over the 100-180E longitude band. The results show large latitudinal movement of cirrus cloud cover with the changing seasons. The examination of the vertical distribution of cirrus clouds shows the maximum of cirrus top-altitude occurrence frequency of approximately 11% at 16 km in the tropics. There are no significant differences in vertical distributions of occurrence frequency of cirrus clouds in the Northern and Southern hemispheric midlatitudes. At latitudes 20N to 60N, the maximum frequency of the cirrus top and base altitudes is about 5.1% at 11 and 8 km, respectively.