In Poland, rural households are encouraged to diversify their activities both in and outside the agricultural sector in order to stabilize and improve their income. However, relatively few households appear to do this. This paper addresses this issue, investigating the returns from the income strategies of rural households using propensity score matching methods and extensive data sets for 1998–2008. The results suggest that returns from combining farm and off-farm activities are lower than returns from specialization, namely, concentrating on either farming or off-farm activities. The income difference between farmers and those who combine farming and off-farm activities increased after Poland joined the European Union.