The purpose of this paper is to present the equilibrium level of unemployment in Poland and examine whether the changes in it affected the degree of restrictiveness of monetary policy between 1998 and 2009. An estimation based on the flow methods within those years, showed that the equilibrium level of unemployment, shifted in the same direction as the actual rate of unemployment. This may indicate the occurrence of hysteresis effect in unemployment in the Polish economy; however, this hypothesis requires a separate analysis. In addition, What's more, during almost the whole period (except for 2001) the level of the actual unemployment rate exceeded the level of equilibrium unemployment. This may suggest that the monetary policy conducted by the NBP was too restrictive. An analysis of the MCI indices showed that the degree of restrictiveness of monetary policy was changing over the period stance. During that time there was a very weak negative correlation between MCI index (which measures the degree of restrictiveness of monetary policy) and the level of equilibrium unemployment.