Theophylline monohydrate and polymorphs of anhydrous theophylline are being compared. Crystallographic data was obtained using the Cambridge structural data source. In this investigation, 1,3-Dimethyl-3,7-dihydro-1H-purine-2,6-dione monohydrate (Ref-code: THEOPH) and 1,3-Dimethyl-3,7-dihydro-1H-purine-2,6-dione (Ref-code: BAPLOT) are chosen. Hirshfeld surface tools were used to visualize the different types of intermolecular interactions throughout the crystal range of theophylline monohydrate and polymorphs of anhydrous theophylline. The fundamental distinction between theophylline monohydrate and anhydrous theophylline appears to be the N—H...O bond dimer. Some other weak interactions distinguish the molecular packing. After the creation of two N—H...O hydrogen bonds, the theophylline dimers that make up the theophylline monohydrate structure are joined by an inversion center. Because of these dimers and having a lagre percenrage of hydrogen and oxygen interactions theophylline monohydrate has a distinctive structure and better tabletability than anhydrous theophylline.