The use of solar energy in thermal desalination processes is one of the most promising applications of renewable energies to seawater desalination. A solar distillation system may consist of two separated devices - the solar collector and the distiller - or of one integrated system. The first case is an indirect solar desalination process, and the second one is a direct solar desalination. This paper deals with indirect solar desalination and its perspectives in the future. First, a summary of existing plants was given. Second, different technologies were compared. Finally, the possible improvements of thermal solar and seawater distillation technologies were considered in order to analyze the perspectives of the competitiveness of solar vs. conventional energy in seawater desalination.