Rainfall shortages constrain small-holders' agricultural production in developing countries and with ongoing climate change these shortages may increase in volume and frequency. Rainwater harvesting irrigation is an interesting technology that decreases this risk. Therefore, one would expect an increasing use of this technology in drought-prone areas, particularly for large and wealthy farms. This study investigated the relation between farm size and share of irrigated land among smallholders from two regions in Ethiopia. It also analyzed which factors explain the share of irrigated land using panel data collected in 2005 and 2010. A random effects tobit model was estimated for the share of irrigated land as a function of variables affecting returns, market prices, source of finance, and expectation formation. The findings show that the share of irrigated land declines with farm size. Moreover, the share of irrigated land depends on distance to market, ease of selling output, age, aridity, distance from natural water sources, credit access, and regional differences. These results question the relevance of water harvesting for farm enlargement. However, they also show that by safeguarding the availability of credit and improving local infrastructure farmers may extend the share of land irrigated by harvested water. (C) 2017 Elsevier Ltd. All rights reserved.