Background: Many frail elderly and disabled persons have to use a manual wheelchair to remain mobile and active. Apart from a well-fitted wheelchair, an appropriate wheelchair cushion is considered crucial for postural support and to prevent complications.Aim: To examined the effect of two types of seat cushions in two types of wheelchairs with regard to pelvic rotation, respiratory function, and interface pressure.Material and methods: Forty healthy elderly between 67 and 85 years of age participated. Two types of commonly used manual wheelchairs and two types of seat cushions were tested. Interface pressure, pelvic position, and respiratory function were measured using a sensor array mat, a study-specific inclinometer, and a spirometer.Results: Differences in interface pressure and pelvic rotation between cushions were found in both wheelchairs. Compared with sitting on a standard cushion, sitting on the positioning cushion increased peak pressure. The posterior pelvic tilt increased with the positioning cushion in the Etac Cross wheelchair and for both cushions in the Etac Cross wheelchair compared with the HD Balance wheelchair. No difference was observed in respiratory function.Conclusions: This study highlights the importance of a thorough evaluation of the effects of wheelchair interventions, especially for the elderly and disabled.