Quantitative T1-mapping might represent an efficient tool to monitor inflammation, necrosis or fibrosis processes in skeletal muscle tissues affected by neuromuscular disorders. However, standard T1-mapping sequences cannot separate the contribution of water and fat protons. If directly applied to fatty infiltrated skeletal muscles, a “global” T1 value would mainly reflect the degree of intramuscular fat and the other underlying processes would largely be hidden. Here, we proposed an optimal sequence allowing simultaneous estimation of water T1 and fat fraction. It was validated in phantom and in vivo acquisitions were performed on several subjects suffering from different neuromuscular diseases.