The low surface brightness galaxies (lsb) have been cataloged selecting them from photographic plates applying subjective criteria. In this work we have tried to determine limit values for parameters, which are independent of the distance, in order to be able to classify quantitatively those objects. Using samples of "normal" and "lsb" (from the DDO catalog) galaxies, we have found that the latter are characterized by a HI velocity profile width, corrected for inclination of less than 224 km/s and a de-projected surface brightness L/A² of less than 2.5x10⁷ L₀/kpc².