We explored the effects of maturational plasticity on motor activations for the affected hand in patients with unilateral lesion involving the rolandic cortex. Ten patients with early lesion (onset < 4 years), seven patients with late lesion (onset > or = 10 years) and eight normal adults underwent [15O]-water positron emission tomography (PET). Rolandic activations in the contralesional hemisphere were enhanced in both patient groups when compared to normal adults. Secondary motor and frontoparietal nonmotor cortices were more activated in the early than in the late lesion group, suggesting a greater potential for reorganization during early development than later in life. Cerebellar activations were similar in late lesion patients and normal adults, but significantly weaker in early lesion patients.