The articleexaminesthe supply-side impact offiscalpolicyonfluctuations in economic trendsin Poland. The analysisis basedon the real business cyclemodel with indivisiblelabor developed by American economist Gary D.Hansen. This model was adapted tothe conditions ofthe Polish economy andexpanded to includeassumptionsaboutfiscalpolicy on the basis of datafrom the1995-2009period. According to the author, the model reflectsthe correlationsbetween GDPandothervariables. However, the negativecorrelationbetweengovernment spendingandconsumption resulting from the model is not confirmed by actual data, Krajewski says. Simulations showthatan increasedshareof capital expenditure in government spending has apositiveimpact onthe economy because it leads to anincrease inproduction,consumption, employment and the level of capital. Themodelalsoshowsthat even though a countercyclicalfiscal policy reducesfluctuationsin production,itleads togreatervolatilityof capitaland consumption. Moreover,the resultsof the model show that if public consumption becomes a strong substituteof private consumption, an increase in government expenditure has a low supply-side impact on thelevel of production, the author concludes.