One of the possibilities of explanation of persistent hypertension after adrenocortical adenoma excision in patients with Conn syndrome could be analysis of transcriptional activity of genes encoding aldosterone synthesis pathway enzymatic proteins within these tumours.The aim of the study was to analyze the expression of mentioned genes in adrenocortical adenomas in patients with primary hiperaldosteronism and to analyse correlations between their expression and results of hormonal tests of blood serum before surgery as well as maximal values of blood pressure before surgery and their decrease after operation.Material and methods. Thirteen patients with Conn syndrome subjected to surgical excision of adrenocortical tumour were analyzed. Expression of CYP 11A1, CYP 21A2, CYP 11B2 and HSD 3B2 genes in tissue of removed tumours was analyzed using RT real-time PCR method. GAPDH was used as reference gene. The results analysis was based on amplification threshold values CT. Analysis of clinical consequences of adrenalectomy was performed after a period of minimum 12 months after surgery.Results. Expression of mRNA, presented as 2-ΔΔCT, of CYP 11A1 gene was 1.58 (1.01-2.48), CYP 21A2-2.74 (1.78-4.24), CYP 11B2- 19.15 (11.28-32.50) and HSD 3B2-2.57 (1.47-4.50). Correlation analysis revealed only negative correlation between CYP 11A1 gene expression and plasma renin activity in upright position (r=-0.604; p=0.049) and positive correlation between HSD 3B2 gene expression and decrease of maximal values of systolic blood pressure in long term follow up (r=0.763; p=0.010).Conclusions. High expression of genes encoding aldosterone synthesis pathway enzymatic proteins is observed in adrenocortical adenomas in patients with Conn syndrome. The transcriptional activity of the genes does not correlate with results of preoperative hormonal tests and is not a prognostic factor of persistent hypertension after adrenal tumour excision.