The purposes of this research were to measure the cost efficiency of sample hazelnut (Corylus avellana) farms and to explore determinants of economic efficiency in the eastern Black Sea region of Turkey. Data envelopment analysis (DEA) was used to estimate efficiency measures of sample farms. Farm managers from 151 randomly selected farms were interviewed for farm-level data between production periods in 2005 and 2006. Research results revealed that inefficient hazelnut farms would have needed to lower production costs by 44% to perform as well as other similar best practice farms. The analysis of the measures of technical efficiency showed that pure technical inefficiency was the primary cause of technical inefficiency. The results also showed that one of the most important positive factors in economic efficiency was sucker control. The age and education level of operators and credit use were the other influencing factors in economic efficiency. Strategies for a better farm-level education, farm extension programmes focused on sucker control, and providing farmers with greater access to credit may help to increase economic efficiency of hazelnut farms.