BACKGROUND: The aim of the present paper was to investigate 20 pediatric patients with cerebral palsy and secondary osteoporosis and consider the efficacy, influence and index of treatment. METHODS: A total of 10 boys and 10 girls, age 1-16 years (mean 7.6 years) with secondary osteoporosis and cerebral palsy treated for 6 months, were studied. Bone mineral density (BMD) was measured. The bone turnover markers were measured just before and 4 months after treatment or at the time of early discontinuation of treatment. The treatment was classified into two groups: vitamin D (alfacarcidol) only; and with bisphosphonate (risedronate). RESULTS: Monotherapy with alfacarcidol was effective for secondary osteoporosis in children, but when used in combination with risedronate it was even more effective in improving BMD. In the two groups, bone-specific alkaline phosphate (BAP) decreased from pretreatment to post-treatment assessment in all but one case, but there was no significant correlation in the difference in DeltaBAP with DeltaBMD. DeltaBAP assumed changes in BAP in treatment either before or after, and DeltaBMD also assumed changes in BMD. N-telopeptides of type I collagen (NTX)/Cr decreased in all cases. The correlation of DeltaNTX/Cr with DeltaBMD was not significant. The therapy and its efficacy did not correlate to the patients' age, sex, medicine regimen or enteral nutrition. CONCLUSIONS: Risedronate therapy is effective for patients presenting with secondary osteoporosis with cerebral palsy. Moreover, it is desirable to treat patients more aggressively from the early stage because risedronate is not affected by the patients' other factors.