The aim of this study was to assess the long-term outcomes of pituitary adenoma residue and the probability of recurrence after complete resection. This retrospective cohort study analyzed patients who underwent surgery due to non-functional pituitary adenoma (NFPA) between 2005 and 2018 at the Clinic for Internal Medicine of the University Hospital Center Zagreb. The dynamics of tumor residue growth or recurrence were monitored postoperatively through MRI scans and data collected from patients' medical records. The study included 130 patients, the majority of whom were male (N=85, 65,4%). The median age of the patients was 57 (range 18 – 78). The average follow-up time for patients was 90.5 months (range 36 – 223). Postoperative residue was observed in 65.4% of patients, and among 45 patients who had complete resection of the tumor, 10 (22,2%) of them had a tumor recurrence during post- operative follow-up. Analyzing groups of patients with progressive and stable NFPA residues, a statistically significant difference was observed in the age of patients and Ki-67 values. However, there was no statistically significant difference in tumor size or invasion of the cavernous sinus between these groups. In patients with complete resection of NFPA, recurrence was recorded in 22.2% of patients, but there were no significant differences in age, gender, or invasion of the cav- ernous sinus compared to the group without recurrence. However, this group had a significantly longer follow-up time (p=0,05). In conclusion, due to the lack of clear predictive factors for residue growth or recurrence, it is necessary to monitor patients long-term with regular MRI scans to timely detect the need for new therapeutic interventions and reduce the possibility of potential tumor growth complications.