Background: Patients with chronic stroke often shows decreased trunk muscle activity and trunk performance. To resolve these problems, many trunk stabilizing techniques including the abdominal drawing-in maneuver (ADIM) and the diaphragmatic breathing maneuver (DBM) are used to improve trunk muscle strength. Objects: To compare the effects of the ADIM and the DBM on abdominal muscle thickness, trunk control, and balance in patients with chronic stroke. Methods: This was a randomized controlled trial. Nineteen patients were randomly allocated to the ADIM (n1=10) and DBM (n2=9) groups. The ADIM and DBM techniques were performed three times per week for 4 weeks. The thicknesses of the transversus abdominis (TrA), internal oblique muscle, and external oblique muscles on the paretic and non-paretic sides, Trunk Impairment Scale (TIS) score, and Berg Balance Scale (BBS) score were used to assess changes in motor development after 4 weeks of training. Results: After the training periods, the TrA thickness on the paretic side, TIS score, and BBS score improved significantly in both groups compared to baseline (p<.05). TIS score was significantly greater in the DBM group than in the ADIM group (p<.05). Conclusion: This study demonstrated that ADIM and DBM are beneficial for improving TrA muscle thickness in the paretic side, trunk control, and balance ability. Intergroup comparison revealed that TIS score was significantly improved in the DBM group versus the ADIM group. Thus, DBM may be an effective treatment for low trunk muscle activity and performance in patients with chronic stroke.