Purpose To compare the effect of 90‐ and 360‐degree selective laser trabeculoplasty (SLT) as primary or supplement therapy in patients with glaucoma and ocular hypertension (OHT). Methods Patients (>30 years old) with OHT, primary open‐angle glaucoma (OAG), pigmentary glaucoma or pseudoexfoliative glaucoma were enrolled in a prospective randomized clinical trial. Patients were sequentially randomized to either 90‐ or 360‐degree SLT. Their intraocular pressure (IOP) was monitored. Results The survival periods (in days) of the two extents (90 or 360 degrees) of treatment were not statistically significantly different (p = 0.85); only pretreatment IOP level could predict survival of treatment (p = 0.02). Conclusion The 90‐degree SLT is as effective as 360‐degree SLT. Further studies are warranted to confirm the findings. High baseline IOP could be a factor that predicts treatment success.