Two remote sensing techniques used to measure water vapor content in the atmosphere are presented: the Lidar/Dial technique and the GPS data analysis method. The dial method, as is well known, can be used to obtain range resolved measurements or an average concentration measurement on the long path using a target topographic method. This methodology permits measurement of the concentration of atmospheric trace gases and, in particular, water vapour profiles. The second remote sensing method is based on an application of the GPS (Global Positioning System). It enables the assessment of the signal propagation delay from satellites to ground-based receivers. Once ground temperature and atmospheric pressure are measured and the GPS signal delay is known, then an estimate of the columnar water vapour content can be performed. In this paper a comparison between the two remote sensing techniques of water vapour measurement are present.