Starting from 2008 the CMS experiment will produce several Petabytes of data each year, to be distributed over many computing centers located in many different countries. The CMS computing model defines how the data has to be distributed in a way that CMS physicists can efficiently run their analysis over the data. CRAB (CMS Remote Analysis Builder) is the tool, designed and developed by the CMS collaboration, that facilitates the access to the distributed data in a totally transparent way. The tool's main feature is the possibility to distribute and and to parallelize the local CMS batch data analysis processes over different Grid environments without any specific knowledge of the underlying computational infrastructures. More specifically CRAB interacts with both the local user environment, with CMS Data Management services and with the Grid middleware.