Decisions taken by the economic authorities within the monetary and fiscal policy influence each other and thus affect the economy of a given country. The literature on the subject indicates that it is essential for the economy that the monetary and fiscal authorities cooperate with each other. However, such coordination of actions of economic authorities is not easy to achieve because the central bank seeks to ensure price stability, while the government strives to maintain high economic growth and a low unemployment rate. In addition, it should be emphasized that the decisions of economic authorities are made at various stages of the business cycle, which may also affect a degree of coordination of monetary and fiscal policy (policy mix). The aim of the article is to identify the relationship between economic variables in the monetary and fiscal policy and thus variables describing the economy in Poland in 2000 - 2018. Particular attention is paid to the following economic variables: GDP per capita, unemployment rate, General Government debt and deficit, investment rate, the main interest rate of the central bank or inflation. The article verifies the hypothesis that variables from the monetary and fiscal policy statistically significantly interact with each other and thus influence the economic variables in Poland. The research methods were based on statistical analyzes. The contribution of this article consists in presenting a role of monetary and fiscal policy in influencing the Polish economy in the years 2000 - 2018.