Seven children with spastic diplegic cerebral palsy and 14 age- and gender-matched nondisabled children participated in the present study for an investigation and comparison of their static standing balance under altered sensory environments. The type of visual input (full, occluded, or sway referenced vision) and the type of somatosensory input (fixed or compliant foot support) were varied factorially to give six sensory environments. Each participant was tested barefooted for 30 s under all six conditions. A force platform collected the ground reaction force, from which standing balance was calculated as the sway area of the center of pressure. The results showed that when somatosensory information was reliable (fixed foot support), there was no significant difference in stance stability between the children with spastic diplegic cerebral palsy and their matched controls, and both types of children were equally affected by the type of visual input. However, when somatosensory information was unreliable (compliant foot support), the difference in stance stability between the children with spastic diplegic cerebral palsy and their matched controls was significantly greater when the visual input was deprived (occluded) or unreliable (sway referenced) than when it was reliable. These results suggest that the children with spastic diplegic cerebral palsy may have difficulties in resolving intersensory conflicts for maintenance of standing balance, or the demands of motor control in sensory conflict conditions outweigh the motor ability of children with spastic diplegic cerebral palsy.