The present invention relates to salts of a pyrrolopyrimidinone derivative having superior PDE-5 inhibition activity and a process for preparing the same. More particularly, the present invention relates to a crystalline acid addition salt prepared by reacting a pyrrolopyrimidinone derivative with an acid selected from gentisic acid, maleic acid, citric acid, fumaric acid and tartaric acid. With no hygroscopic property and superior long-term storage stability, photostability and thermal stability, the salts of the pyrrolopyrimidinone derivative are appropriate to be prepared into medications and, with superior PDE-5 inhibition activity, are useful for the treatment and prevention of erectile dysfunction, pulmonary arterial hypertension, chronic obstructive pulmonary disease, benign prostatic hypertrophy and lower urinary tract diseases.
