Does geomagnetic storm magnitude depend on solar flare importance?

In order to predict space weather effects, solar flares are often used as precursors of magnetic storms on the Earth. In particular, possible relation between the solar flare importance and magnetic storm intensity is discussed in some papers. However, published results contradict each other. We compare the published results on the flare-storm dependence and discuss possible causes of this disagreement: (1) different intervals of observation, (2) differing statistics, and (3) different methods of identification of events and their comparison. Our analysis has shown that the fact of occurrence and the magnitude of a geomagnetic storm cannot be determined, generally, using only the solar flare importance. However, analyzing additional information on the coronal mass ejection (CME), associated with the geomagnetic storm, one can offer an algorithm for the storm magnitude prediction on the basis of flare importance.