Quercetin is a plant-derived flavonoid known to possess anti-inflammatory property, but its use as a chemopreventive substance has been reviewed quite recently. A number of reports have assessed the pro-apoptotic action of quercetin in cancer cells, which contributes to the chemopreventive action of food, similar to many other flavonoids. Quercetin is a forthright inhibitor of PI3K, NF-B, and other kinases involved in intracellular signaling. However, a possible selective intracellular target for quercetin has still not been focused on. The challenge is to highlight an eligible target in order to address possible natural compounds, either in food extracts or as pharmaceuticals, as real drugs against cancer.