The aim of this study was to evaluate the potential of magnetic resonance mammography (MRM) to distinguish inflammatory breast carcinomas (IBC) from acute mastitis (AM). This study compared MRM examinations of two selected groups of patients: 48 subjects with IBC and 42 patients with AM. No statistical differences were revealed between the two groups for morphology of masses and of non-mass-like enhancement, breast enlargement, diffuse skin thickening, abnormal nipple configuration, prominent vessels, and also for cutaneous/subcutaneous, perimamillar and diffuse oedema. However, initial and postinitial dynamic characteristics significantly differed between the two groups (p < 0.001). In IBC, more masses with a greater average size were detected (p < 0.05). The following morphological criteria were also observed more often in IBC (p < 0.05): T2-hypointensity of masses (77.5%/18.2%), blooming sign (62.5%/31.8%), infiltration of pectoralis major muscle (interruption of fat plane: 54.2%/16.7%; pathological enhancement: 33.3%/7.1%), perifocal (66.7%/33.3%), prepectoral (72.9%/31.0%) and intramuscular pectoral oedema (41.7%/7.1%). The main localisation of AM was subareolar, of IBC central or dorsal (p < 0.001). The discrimination between AM and IBC remains a diagnostic challenge because of overlapping imaging features. However, the combination of multiple dynamic and morphological MRM criteria seems to have the potential for a differential diagnosis.