Background <p>Mental chronometry tests, including upper and lower extremity functions, evaluate the temporal congruence component of motor imagery. This study aimed to compare the utilization of upper and lower extremity functions in mental chronometry tests.</p> Methods <p>This study included 70 individuals with multiple sclerosis and was designed based on an a priori power analysis. Mental chronometry tests, including the Box and Block Test (BBT) and the Timed Up and Go Test (TUG), were administered, and execution times, motor imagery times, and mental chronometry ratios were compared between the most and least affected extremities.</p> Results <p>A significant difference was observed in execution times between the most and least affected extremities in BBT (<i>p</i> = 0.001). Similarly, motor imagery times in BBT were significantly different between most and least affected extremities (<i>p</i> = 0.009). However, no significant difference was found in mental chronometry ratio between the most and least affected extremities (<i>p</i> = 0.179). Comparisons between upper and lower extremity tests revealed that the mental chronometry ratio was significantly higher for BBT than for TUG test in both the most affected and least affected extremities (<i>p</i> = 0.001).</p> Conclusion <p>Individuals with MS showed differences in imagery–execution congruence between upper- and lower-extremity mental chronometry tasks, with higher congruence observed in the upper-extremity task. These findings support a task-specific interpretation of motor imagery performance rather than a generalized advantage of upper-extremity motor imagery.</p> Trial registration <p>Not applicable. This study was observational and did not involve a clinical trial registration.</p>