The microenvironment of solid tumors is heterogeneous, and hypoxia is associated with the malignancy of cancers. In this review, we introduce the characteristics of cancer cells in hypoxic areas. The hypoxic response of cancer cells in vivo is different from that in vitro. The expression of MYC is downregulated in the cancer cells in hypoxic regions. Cancer cell proliferation and its metabolism are dramatically suppressed in the hypoxic area, and are in a stage of cellular dormancy. Dual deficiency of oxygen and glucose in vitro induces dormancy of cancer cells in hypoxic regions. Researchers have focused on the proliferation of cancer cells so far, but aside from proliferation, it is important for the survival of cancer cells that they become inactive/ dormant in the hypoxic regions. Dormant cancer cells become resistant to chemotherapy and irradiation, leading to recurrence and metastasis. Therefore, we need to characterize and target dormant cancer cells in the hypoxic regions.