Abstract Objective: To investigate the effects of Δ9-tetrahydrocannabinol, the principal psychoactive compound of Cannabis sativa, and cannabinol, a Δ9-tetrahydrocannabinol degradative product, on human non-small cell lung cancer cells. Methods: Δ9-Tetrahydrocannabinol and cannabinol were tested for anticancer activity in human non-small cell lung cancer (A549) cells. The effects on cell proliferation, apoptosis, and phosphorylation profiles were examined. The effects of Δ9-tetrahydrocannabinol and cannabinol on tumor growth were also investigated using a xenograft nude mouse model. Apoptosis and targeted phosphorylation were verified by immunohistochemistry. Results: Δ9-Tetrahydrocannabinol and cannabinol significantly inhibited cell proliferation and increased the number of apoptotic cells in a concentration-dependent manner. The Δ9-tetrahydrocannabinol- and cannabinol-treated...