Virtual Reality (VR) technology combined with eye-tracking offers new possibilities for objective assessment of attention-related disorders. This proof-of-concept study investigates whether eye vergence measurements in immersive VR environments can differentiate individuals with ADHD from neurotypical controls during Go/No-Go tasks. A serious game was developed using Unity and HTC Vive Focus 3 with integrated eye-tracking, implementing two interaction modalities (gaze-only and controller-based). The system calculates real-time ocular vergence angles based on interpupillary distance and object coordinates in the virtual environment. Eleven adults participated: one individual with clinically diagnosed ADHD and ten neurotypical controls. Despite the limited ADHD sample size, the participant with ADHD showed consistently elevated vergence angles across all conditions ( \(\textit{p < 0.001}\) ), with effect sizes ranging from negligible to large (Cohen’s d: –0.188 to –0.952). While these preliminary findings suggest potential differences in vergence patterns, substantial replication with larger clinical samples is essential before considering any diagnostic applications. This work establishes a methodological foundation for integrating VR-based eye-tracking in ADHD research and demonstrates the technical feasibility of real-time vergence analysis in immersive environments.