Abstract Repetitive transcranial magnetic stimulation (rTMS) has been developed as a novel tool for modulating cognition by delivering stimulation in the brain. However, the effects of rTMS on cognition are still controversial. This randomized, sham-controlled, crossover study was designed to determine whether rTMS of the left dorsolateral prefrontal cortex (DLPFC) interferes with the Go/NoGo task and whether personal parameters such as age affect rTMS. A total of 24 healthy subjects (12 male and 12 female, aged 20–37 years) underwent one session of active rTMS followed by sham rTMS (total of 1600 pulses, 100% of motor threshold, 5 Hz, 8 s), or vice versa. The results did not show any differences between active and sham rTMS stimulation in terms of performance accuracy, response speed, or choice reaction time (cRT) implicating that short-term rTMS will not enhance or deteriorate cognition. However, percentage cRT shortening induced by active rTMS was negatively correlated with age ( r=−0.57, P=0.005), whereas that induced by sham rTMS was not ( r=−0.23, P>0.05), suggesting that cognition of younger subjects might have greater modulation by active stimulation than older ones. This finding may help explain some of the controversies or paradoxical results observed in studies of the effect of left DLPFC rTMS on cognition.