One of the most comprehensive approaches to explaining attention-deficit/hyperactivity disorder (ADHD) symptoms is Barkley's behavioral inhibition model (BBIM) (1997), in which behavioral inhibition (BI) plays a primary role. Due to the substantial role of working memory (WM) in explaining ADHD symptoms, Barkley recently updated his model and elevated WM from a mediator variable (in BBIM) to a primary position as an exogenous variable alongside BI, and titled his new model as Barkley's updated executive functioning model (BUEFM). However, since the information about the explanatory power of the new model is sparse, this study aims to investigate the impact of this change in WM role by comparing these two models to explain ADHD symptoms. The study involved a sample of 184 (96 females and 88 males) undergraduate students with high ADHD symptoms who were selected using the purposive sampling method. For assessing models, we have utilized four tools that include: CNS-Vital Sign Test Battery
Barkley Deficit in Executive Functioning Scale
self-verbalization questionnaire (SVQ)
and trail making test. We analyzed the data by running structural equation modeling (SEM) analysis using IBM AMOS software version 22. The results show that Model Comparison Measurement (e.g. AIC was 197.583 and 144.614 for BBIM and BUEFM, respectively) and Model Fit Indices (e.g. root mean square error of approximation (RMSEA) obtained 0.076 and 0.067 for BBIM and BUEFM, respectively) representing that BUEFM had a better value than BBIM, which means that the BUEFM was considered better fitting to the data. The findings of this study show that BUEFM has more Predictive power than BBIM to predict symptoms of ADHD through the motor control fluency (MOT) variable.