This article proposes the classification of farms of natural persons according to the level of farm income per unit of work of a farmer and farmer's family members. One hour of family labour was adopted as such unit. According to this criterion, farms were divided into three classes. In the first one, the unit income is lower than the average payment for employed labour in agriculture. In the second one, this income is higher than the average payment for employed labour in agriculture but lower than the average payment for labour in the national economy. Farms of the third class allow earning income higher than the average payment for labour in the national economy. Those from the first class are called auxiliary farms, from the second – transitional, and from the third – developmental. The research included a panel of 5471 farms with economic size above EUR 4 thousand SO and covered by the monitoring of the Polish FADN in 2009-2017. The average share of auxiliary, transitional and developmental farms in the analysed period amounted to 31.2%, 12.1% and 56.5%, respectively. Auxiliary and transitional farms did not show the ability to develop. Developmental farms showed this ability. It was estimated on this basis that in 2016 there were 147.2 thousand of them in Poland, which means that the share of this group in the national population of farms owned by natural persons was 10.6%.