Genetic relationships among 18 Turkish hazelnut (Corylus avellana L.) cultivars were investigated using randomly amplified polymorphic DNA (RAPD), intersimple sequence repeat (ISSR), and amplified fragment length polymorphism (AFLP) markers. Twenty-five RAPD primers, 25 ISSR primers, and eight AFLP primer pairs generated a total of 434 polymorphic marker loci. The three marker systems were able to differentiate the cultivars. Genetic similarity, index values ranged from a high of 0.96 for 'Kan' and 'UzunMusa' to a low of 0.73 for 'Yassi Badem' and 'Kalinkara'. The genetic relationships were presented as an unweighted pair group method with arithmetic average (UPGMA) dendrogram and a three-dimensional principal coordinate analysis (PCoA) plot. The UPGMA dendrogram showed two main clusters, while PCoA analysis showed three groups. Cultivar-specific markers were produced by all marker systems for 10 cultivars. This study demonstrates the usefulness of molecular markers for identification of hazelnut cultivars.