We measured the difference of sitting pressure between the affected and unaffected sides (DSPAU) using sitting pressure measured with a force platform to identify sitting imbalance. The aim of this study is to investigate the relations between sitting balance and functional status or parameters according to characteristics stroke patients. We examine changes in DSPAU and functional assessment before and after a 3 week of rehabilitation in hemiplegic stroke patients (n = 73). These pre- and post-treatment data according to stroke characteristics, and correlations between the DSPAU and functional scales were analyzed. The DSPAU was greater in the non-ambulatory group compared to the ambulatory group, in patients who scored lower in the Medical Research Council (MRC) scores, and in patients whose the MRC scores for the lower limbs were lower than of the upper limbs. We observed that a decrease in the DSPAU was associated with an improvement in functional assessment parameters following rehabilitation. Further, changes in DSPAU were significantly correlated to the Modified Barthel Index. We observed that a decrease in DSPAU was associated with an improvement in functional parameters following rehabilitation. In conclusion, repeated measurements of sitting balance using DSPAU may be helpful to predict motor and functional recovery in stroke patient with hemiplegia.