This study investigated characteristics of interface pressure distribution of right and left hemiplegia (rt-hemi and lt-hemi), paraplegia (para), quadriplegia (quadric), and normal subjects (normal) during wheelchair seating. A total of 73 subjects were participated in this study. Maximum interface pressure, mean interface pressure, and interface pressure gradient in the right and left sides of buttocks were measured for 30 minutes while minimizing possible movements of participants and using a same manual type wheelchair with a fabric seat. The ANOVA was performed using the data measured at the end of the test. There were substantial differences in the mean interface pressure on the buttocks between rt-hemi and lt-hemi. The maximum interface pressure on the buttocks was significantly high in hemi, para and quadric compared to normal. A statistically significant difference in the maximum interface pressure gradient on the buttocks as found between paralytic patients and normal people. Based on these results, a new approach for developing seat cushion orthosis to prevent decubitus ulcer is required for even distribution of interface pressure considering individual paralytic characteristics. In addition, the maximum interface pressure and gradient on the buttocks could be used as a useful clinical-biomechanical guideline in developing a seat cushion orthosis for preventing decubitus ulcer of paralytic patients.