This thesis describes the study of the isotopes of hydrogen and helium and of the boron and carbon nuclei in the cosmic radiation. New measurements of the fluxes of 1H, 2H, 3He, 4He, between 120 MeV/n and 900 MeV/n, and of the boron and carbon fluxes, between 400 MeV/n and 120 GeV/n, are presented at the top of the atmosphere. The measurements were made with the space-borne PAMELA experiment from July 2006 to March 2008, that is during a period of minimum solar activity and negative solar magnetic field polarity. Such measurements can help in achieving a more detailed knowledge of the physics of cosmic ray propagation inside the Galaxy, which is a key ingredient in interpreting cosmic ray origin, acceleration mechanism and the possible presence of new physics.
