Background: In the present study, we sought to describe a procedure for the creation of co-registered positron emission tomography (PET) and magnetic resonance imaging (MRI) polar plots of cardiac PET/MRI examinations, validate the resulting plots against available standard methods in patients with myocardial infarction and provide examples that demonstrate the advantage of the novel approach over existing standards. Methods: Co-registered LGE and PET short-axis images were transformed into polar maps based on a radial sampling pattern. LGE was automatically detected using an automated thresholding algorithm (ATA). In 20 PET/MRI examinations in patients with acute myocardial infarction, agreement between manual LGE assessment and the ATA classification was calculated. Also agreement between MRI-segmentation based PET polar plots and standard PET polar plots (created with the Corridor4DM software package) was assessed. Results: No statistically significant difference in infarct sizes between manual and ATA segmentation was found (p = 0.12). Both methods were highly correlated (Pearson’s r = 0.96, p < 0.01). Bland-Altman analysis revealed lower and upper limits of agreement of - 4.7 g and 3.6 g. Agreement between MRI-segmentation based PET polar plots and standard PET polar plots was very high (mean kappa of 0.91 ± 0.10; p < 0.01 in all cases). In three additional patients with myocardial inflammation, the software successfully created polar plots that demonstrate the location and extent of pathologic tracer uptake in the left ventricular myocardium. Conclusion: A straightforward software approach for the creation of co-registered PET and MRI polar plots was described and successfully demonstrated in PET/MRI studies of myocardial infarction and inflammation.