The scale efficiency enables to measure technical relationship between farm size and efficient land using as a basic production factor  according to its different allocation. The research has been done on a selected sample of agricultural enterprises in the Slovak Republic. A non-parametric data envelopment analysis approach has allowed investigating the differences in efficiency among various size groups of 110 agricultural enterprises. The research has proved that about 10 per cent of the analysed farms were operating during the analysed period at the optimal scale, 77 per cent at the above optimal scale and 13 per cent of the farms could increase the efficiency by increasing their acreage of agricultural land.