A case of an 8-year-old girl with unilateral retinoblastoma is presented. The clinical picture was dominated by inflammatory signs and retinal detachment. Ultrasonographic A/B-scan showed a funnel-shaped total retinal detachment and a thick solid mass with similar shape just behind it. The main characteristics of the mass were: irregular inside echo pattern, medium high internal reflectivity, no sign of vascularity, no after movements following a sudden ocular movement, and no shadowing of the scleral or orbital tissues behind it. The vitreous cavity in front of the retina and behind the mass was ultrasonographically clear. The described funnel-shaped echographic pattern might be typical of the diffuse infiltrating retinoblastoma.