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Scintigraphy with 111In-DTPA-octreotide (111In-octreotide) enables the localization of tumours with somatostatin receptors on their cell membranes, of which pituitary adenomas are an example. Trans-sphenoidal excision of such tumours is sometimes incomplete and the detection of post-surgical residues is a difficult diagnostic task. In this study, we used 111In-octeotide SPET to visualize pituitary adenomas and their minimal residues. In positive cases, the indirect demonstration of the presence of somatostatin receptors may be decisive for the planning of treatment. 111In-octreotide SPET was able to visualize adenomas in 21 of 27 patients (77.7) (10 GH-secreting, 10 PRL-secreting and 1 non-secreting). Repeat SPET after the recurrence of clinical symptoms and hormone hypersecretion revealed intense 111In-octreotide uptake by residues in 8 of 10 patients (4 GH-secreting and 6 PRL-secreting). Magnetic resonance imaging was positive in only 3 of these 10 patients. Our results suggest that 111In-octreotide SPET, in combination with other imaging modalities, is useful in the diagnosis and follow-up of pituitary adenomas. It ensures better selection of patients for treatment with somatostatin analogues, both pre- and postoperatively, and assists in the development of personalized treatment plans.