Salt forms of (R)-3-(4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-1H-pyrazol-1-yl)-3-cyclopentyl propanenitrile with maleic acid, or sulfuric acid or phosphoric acid, a method for its production, a composition on its base and use thereof for modulation of Janus kinase activity and are useful in the treatment of diseases related to activity of Janus kinases including, for example, immune-related diseases, myeloid proliferative disorders, cancer, and skin disorders.