Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disorder characterized by a combination of main symptoms: opsoclonus, myoclonus, ataxia, psychoemotional and behavioral disturbances. OMS can develop in children as a result of immunopathological processes against the background of infectious or oncological pathology and lead to persistent neurological deficit. A case of ten-year observation of paraneoplastic OMS associated with neuroblastoma in a child is presented. Within 6 months, the clinical picture of OMS was not full and manifested by recurrent cerebellar ataxia and psychoemotional disorders. The appearance of opsoclonus against the background of increased disturbances in statics and coordination made it possible to diagnose OMS and suggest its paraneoplastic genesis. The peculiarity of the case is the combination of opsoclonus with the development of a symptomatic epileptiform ictus. Surgical treatment of neuroblastoma, immunosuppressive therapy in combination with nootropic and symptomatic anticonvulsant therapy have shown effectiveness and led to stabilization of the condition, regression of cerebellar symptoms and restoration of the rate of mental development. The long course of OMS with the gradual formation of a complete symptom complex complicates timely diagnosis of the underlying disease. Cases of cerebellar ataxia, myoclonus and abnormal eye movements, regardless of the severity and sequence of development of the clinical picture, require an interdisciplinary diagnostic approach and consideration of oncological pathology in a differential diagnostic aspect.