Gingko flavonoids (GFLAs) were isolated from extract Egb761 and radiolabeled with I-131. Quality control and lipophilicity studies for I-131-GFLAs were performed. Cellular incorporation ratios for I-131-GFLAs were investigated. The radiolabeling yield of GFLAs with I-131 was 90.69 % +/- 3.90 and log P value of I-131-GFLAs was 0.99 +/- 0.03 (n = 3). Incorporation of I-131-GFLAs on PC3 and MCF7 cells was satisfactory, whereas higher uptake ratios were observed on PC3 cells. A promising agent for cancer diagnosis is presented.