Cannabidiol derivatives (1, 2 and 3), 5-fluorouracil (4, 5-FU) and adriamycin (5, AM) were tested for their growth inhibitory effects against human tumor cell lines using two different 3-{4,5-dimeth-ylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and sulforhodamine B protein (SRB) assay. The light microscopic study showed morphological changes of the treated cells. Disruptions in cell organelles were determined by colorimetric methods; MTT assay and STB assay. These results suggest that cannabidiol (1, CBD) retains the most growth-inhibitory activity against human tumor cell lines.