Based on neuroscience research, the PETTLEP model was developed by Holmes and Collins (2001). The model provides imagery guidelines which identify seven key factors (physical, environment, task, timing, learning, emotion, perspective) that should be included when developing interventions to maximise functional equivalence. This study explored the effect of a short-term PETTLEP imagery intervention, compared to `traditional' imagery, on a computer game: Need for Speed Underground 2 (EA games). Eighty participants were randomly assigned to one of four groups: PETTLEP imagery group, `traditional' imagery group, physical practice group and control group. After three practice attempts, pre-tests consisted of five attempts at the game. The game involved completing timed laps by manoeuvring a vehicle around a track using the computer's arrow keys. The PETTLEP group completed individualised response training, and then performed imagery sitting in front of the computer screen and repeatedly imaging themselves completing the task. The `traditional' imagery group was sat in a separate room, given individualised stimulus training and instructed to relax and close their eyes during imagery. The physical practice group performed the actual task. Each intervention lasted for forty-five minutes, immediately followed by the post-test, which again consisted of five attempts at the game. A group x test ANOVA showed that the PETTLEP imagery group and physical practice group both improved significantly from pre-test to post-test (p<0.05). However, there was no significant difference in the magnitude of their improvements. The traditional imagery and control groups showed no increase in performance from pre-test to post-test (p>0.05). The results strongly support the use of PETTLEP in enhancing performance on a cognitive task. Contrary to previous studies, PETTLEP was as effective as physical practice. This finding could have important implications for athletes returning from injury, suffering from over-training and for use in pre-performance routines. Therefore, sports psychologists should maximise the functional equivalence of their imagery interventions to have the greatest positive effect on performance on such cognitive tasks, at least in the short term. Future research needs to focus on applying short-term PETTLEP interventions to different tasks, varying in cognitive complexity. Assessing the effectiveness of PETTLEP imagery used in various combinations with physical practice would also be a useful addition to the literature.