INTRODUCTION : Various techniques have been used in an attempt to reduce interfering extracardiac activity in myocardial perfusion imaging with inconsistent results. The aim of this study was to investigate the effect of a combined intervention on the frequency and intensity of interfering extracardiac activity. METHODS : Patients (n=230) routinely referred for a 2-day stress-rest myocardial perfusion examination were assigned randomly to one of two groups. Group A (n=114) received a single intervention (diluted lemon juice) before stress imaging and a combined intervention (diluted lemon juice and soda water) before rest imaging. Interventions were reversed for group B (n=116). Three interpreters, blinded to the intervention, assessed early and delayed planar images from 195 patients in terms of the frequency and the intensity of interfering extracardiac activity. RESULTS : The myocardial to extracardiac (MYO : EXC) ratio between groups for the rest studies was marginally not significant (P=0.060 and 0.059), showing an increase in ratio when the combined intervention was administered. There were significant differences (P≤0.001) in the frequency, intensity, and MYO : EXC ratio between the early and the delayed studies. CONCLUSION : Combining interventions that stimulate radiopharmaceutical hepatic excretion and utilize the volume effect is advantageous in myocardial perfusion imaging, with delayed imaging being advocated as a complementary intervention.