Objective To investigate the effect of heroin abuse on attention switching. Methods Thirty-six Heroin abusers (33 males, 3 females) and 36 controls (32 males, 4 females) were enrolled in the study. Their cognitive function was tested by using the Switching Task, including Sustained Attention trials and Switching Attention trials. The reaction time and accuracy were recorded separately by the computer. Results The accuracy or reaction times were not signifi-cantly different between Switching Attention trial and Sustained Attention trial in heroin abusers, suggesting a lower Switch Costs value compared to the healthy controls [(19.7 ± 66.8) ms vs. (85.1 ± 92.4) ms]. The healthy controls showed faster reaction speed [Sustained Attention trial (695.3 ± 95.9) ms vs. Switching Attention trial (780.3 ± 93.3) ms, P<0.05] and higher accuracy [Sustained Attention trial (98.0%±2.2%) vs. Switching Attention trial (93.8%±5.0%), P<0.05] under the Sustained Attention trial. Compared with the healthy controls, the heroin abusers showed slower reaction speed [(791.6 ± 74.3) ms vs. (695.3±95.9) ms, P<0.05] and lower accuracy [(92.5%±8.4%) vs. (98.0%±2.2%), P<0.05] in Sus-tained Attention trial, but not in Switching Attention trial. Conclusions The present study has revealed absence of Switch Costs in heroin abusers, which may be related to the damage of heroin abusers in their Sustained Attention function.