The effects of Coriolis forces to interfacial stabilities on miscible rotating Hele-Shaw flows are investigated by means of highly accurate numerical schemes. Two major influences on the interfaces, i.e. the stabilization of circumferential fingerings and the unstable body distortion of droplets, are observed. These two phenomena can be represented by two characteristic measurements, i.e. interfacial length and radius of gyration, respectively. Without an additional injection, the miscible interface is found to be more stable at higher Coriolis factors, based on both the judgments of growths in interfacial length and the radius of gyration. However, with an additional injection, a visible body distortion with suppressed interfacial fingerings at higher Coriolis factors leads to inconsistent developments in these two characteristic measurements. The stabilized effect of interfacial fingering delays and weakens the growth in interfacial length at higher Coriolis factors, while faster and greater growth in the radius of gyration is observed because of the significant body distortion. As a result, the effects of the Coriolis forces on the miscible interfacial instabilities should be addressed with great caution. Copyright (c) 2005 John Wiley & Sons, Ltd.