Delta opioid receptors are involved in modulation of nociception, thermoregulation, locomotor activity and rewarding properties of drugs of abuse. The new analog of deltorphin – DK-4 is a peptide with high affi nity to delta opioid receptors in mouse vas deference bioassay. The aim of our study was to indicate whether delta opioid receptors are involved in the rewarding effects of cocaine. Therefore, we tested infl uence of (1) opioid receptor antagonists (μ, κ, δ) on the expression of cocaine-induced conditioned place preference (CPP); and (2) infl uence of DK-4 on the cocaine reinstatement of CPP (Sleipness et al. 2007). Rats were conditioned daily with cocaine (5 mg/kg, i.p.), tested on the 6th day (the expression of CPP), and then retested for 9 days to monitor the extinction of the CPP. On the day 10 animals were treated with a single injection of cocaine (5 mg/kg) or DK-4 (5, 10 nmol, i.c.v.) to reinstate the CPP. Our results indicated that naltrindole – a delta opioid receptor antagonist decreased cocaine rewarding effect (the expression of CPP). DK-4 increased the reinstatement of cocaine-induced CPP. These studies suggest that delta opioid receptors are involved in the cocaine-induced rewarding effects.