Second malignancies develop with increased incidence in patients with herediter retinoblastoma. The most common second malignancies in retinoblastoma survivors are soft tissue sarcoma and osteosarcoma. Lymphoma developing as a second malignancy has rarely been reported. Here we report a case of lymphoma diagnosed in a 13 year-old-boy, 12 years after the diagnosis of unilateral retinoblastoma having heterozygous p.R552 (c.1654C>T) mutation, treated with enucleation and radiotherapy. The risk of second tumour is higher in the hereditary retinoblastoma, especially in cases undergoing external beam radiation therapy.