Objective: To assess the pupil diameters of emmetropes and myopes in photopic, mesopic and scotopic conditions. Material and Methods: Pupil diameters of 49 emmetropic subjects [spherical equivalent (SE) values +/- 0.25 diopter (D) with a mean age of 31.0 +/- 10.5 years (range 17 to 58 years)], and 61 age-matched (mean age 31.3 +/- 8.9 years, range 17 to 52 years) myopic subjects (SE values >=-1D) were measured with the infrared pupillometer integrated within Schwind Sirius Multifunctional diagnostic device (Eye-tech-solutions, Kleinostheim, Germany) in photopic (40 lux) condition simulating the day-time in mesopic (4 lux) condition and in scotopic (0.04 lux) condition simulating the level of light encountered at night. All statistical analyses were performed according to two-sided hypothesis tests and a p-value of less than 0.05 was considered statistically significant. Results: The mean photopic pupil diameter was 3.62 +/- 0.73 mm (range 2.49 to 5.83) in the emmetropic group and 3.86 +/- 0.85 mm (range 2.06 to 6.67) in the myopic group. The mean mesopic pupil diameters were 4.68 +/- 0.78 mm (range 3.19 to 6.45) and 5.16 +/- 0.91 mm (range 3.23 to 7.46) and the mean scotopic pupil diameters were 5.63 +/- 0.70 mm (range 4.28 to 7.14) and 6.08 +/- 0.86 mm (range 4.30 to 7.95) in emmetropes and myopes, respectively. The mean pupil diameters of myopes were larger than emmetropes in all three light conditions (p<0.001). There was no interaction between patient group and light condition (p>0.05). Conclusion: The mean pupil diameters of myopic subjects were larger than the pupil diameter of emmetropes. Pupil diameter should be measured objectively under standardized illumination levels in order to minimize the risk of post-operative glare and halo formation in refractive surgery patients.