Background: Interventional cardiologists are inevitably exposed to low-dose radiation, and consequently are at risk for radiation induced diseases like cataract and left-sided brain tumours. Operator behaviour may possibly be the largest influencer on radiation exposure. We hypothesised that awareness regarding radiation exposure grows as skill and the general experience in the catheterization laboratory increase. Objectives: In this study we determined the difference in the relative radiation exposure of staff interventional cardiologists compared with cardiology fellows-in-training. Methods: During this prospective trial the operator’s radiation exposure (E in µSv) was measured at chest height during 766 diagnostic catheterisations and percutaneous coronary interventions. Also, the patient exposure (DAP in mGy·cm2), representing the amount of radiation administered by the operator per procedure, was collected. The primary outcome of this study was the difference in relative exposure between staff interventional cardiologists versus cardiology fellows-in-training (E/DAP). Results: From January to May 2017, staff interventional cardiologists performed 637 procedures and cardiology fellows-in-training 129 procedures. The performance of relatively complex procedures by staff interventional cardiologists resulted in a 74% higher use of radiation compared with fellows-in-training. Consequently, staff interventional cardiologists were exposed to 50% higher levels of actual radiation exposure. However, when correcting for the complexity of the procedure, by comparing the relative operator exposure (E/DAP), fellows-in-training were exposed to a 34% higher relative exposure compared with staff interventional cardiologists (p = 0.025). Conclusions: In the current study, when corrected for complexity, cardiology fellows-in-training were exposed to significantly higher radiation levels than staff interventional cardiologists during catheterisation procedures.