iv Abstract This thesis investigates the effects of government spend- ing on aggregate economic variables in the Czech Republic. The standard RBC and New Keynesian models assume only forward-looking households despite the evidence of a sig- nificant fraction of non-optimizing households. These mod- els do not provide reasonable predictions for the response of consumption: both models predict its fall following a gov- ernment spending shock. Therefore, a variant of the New Keynesian model, where rule-of-thumb households coexist with optimizing households, is used for the analysis. We have found that fiscal policy has a positive impact on output, although government spending multiplier does not exceed one. Also, the impact on consumption is positive for several periods following a fiscal spending shock, which is consistent with the evidence. JEL Classification: C32, E32, E62 Keywords: fiscal policy, fiscal multipliers, fiscal VAR, rule- of-thumb consumers