Eye-Tracking (ET) is a promising tool for mathematics education research. Interest is fueled by recent theoretical and technical developments, and the potential to identify strategies students use in mathematical tasks. This makes ET interesting for studying students with mathematical difficulties (MD), also with a view on inclusive settings. We present a systematic analysis of the opportunities ET may hold for understanding strategies of students with MD. Based on an empirical study with 20 fifth graders (10 with MD), we illustrate that and why ET offers opportunities especially for students with MD and describe main advantages. We also identify limitations of think aloud protocols, using ET as validation method, and present characteristics of students’ strategies in tasks on quantity recognition in structured whole number representations.