18F-fluorodeoxyglucose positron emission tomography (FDG-PET)/CT is commonly used to assess tumour recurrence in high-risk patients with malignant melanoma (MM). However, results can be ambiguous either because of the CT's insufficient soft-tissue contrast or non-specific FDG accumulation caused by inflammation. Ultrasound (US) can provide additional morphologic information that is superior to CT. For precisely combining PET and US findings, we used a real-time fusion technique based on navigated US (PET/US fusion). Here, we describe our results from patients where PET/US fusion proved helpful in differentiating unclear PET/CT findings. This fusion technique is likely to be helpful for decision making in MM patients and biopsy guidance.