High-density disruptions and low-q disruptions have been investigated by soft-X-ray imaging on the JIPP T-II tokamak. Although an m = 3 / n = 2 mode is identified together with a 2/1 mode before partialdisruptions in high-density discharges, the resulting disturbance is limited and the central region is not affected. The growth of the 3/2 mode detected in low-q discharges leads to a rearrangement of the soft-X-ray profile by a 1/1 mode. The essential feature of major disruptions is the abrupt central thermal quench. Before major disruptions the predominant 2/1 mode is modulated by a central 1/1 component. The 1/1 mode is found to play an important role in the final stage of major disruptions, both in high-density discharges and in low-q discharges.