The present invention relates to a modified release pharmaceutical composition of dexmethylphenidate or salts thereof. In particular, the present invention relates to a modified release pharmaceutical composition comprising plurality of components exhibiting both immediate and extended release of dexmethylphenidate or salts thereof. The composition may provide therapeutically effective plasma concentration over a period of 24 hours to treat attention deficit hyperactivity disorder when administered to a patient in need thereof. The invention also includes process of preparing such composition.