Osteoid Osteoma was first proposed by Jaffe in 1935 to designate a benign condition of bone characterized by the formation of a nidus of vascularized osteoid tissue with sclerosis of sorrounding tissue. Osteoid osteoma has occurred in every bone of the body. Approximately 50 per cent of osteoid osteoma occur in the femur and tibia and osteoid osteoma about the hip joint is rare disease and in growing child, their nonspecific signs and symptoms are inflammatory synovitis, joint effusion, and soft tissue swelling. Scattered cases of osteoid osteoma in the femur neck of the hip joint of the child is to be found in several reports. We experienced a case of osteoid osteoma of the femoral neck with intracapsular nidus simulating an chronic inflammatory synovitis and we had a difficulty in locating the intracapsular nidus due to confusing extracapsular sclerotic area.