The presence of concomitant cardiac pathology exacerbates the course of chronic obstructive pulmonary disease (COPD) and worsens the prognosis for both conditions. Objective — to improving the efficiency of diagnostics and treatment in patients with arterial hypertension and COPD, adding L-arginine to the complex therapy. Materials and methods. A clinical examination was performed on a total of 140 patients, consisting of 82 individuals with arterial hypertension complicated by chronic obstructive pulmonary disease (COPD), and 58 patients with isolated hypertension. Each group was further subdivided into subgroups based on their treatment regimen, which included basic therapy alone, basic therapy along with co-existing pulmonary disease management, and a subgroup receiving basic therapy combined with L-arginine supplementation. Results and discussion. The course of the diseases was more severe in patients with combined pathology. An acute drug test with arginine showed a decrease in blood pressure in both the small and large circles of circulation along with changes in endothelial function. Three months after the complex treatment with L-arginine resulted in the decrease of pressure in the small circle of circulation, had an effect on the structural and functional changes of both ventricles, diminished manifestations of diastolic dysfunction of the heart, increasing the physical activity and endothelium-dependent vasodilation, reduced the activity of anti-inflammatory cytokines in patients with hypertension and COPD. The inclusion of L-arginine as a functional corrector of endothelial function to the basic therapy of patients with arterial hypertension and COPD contributes to the improvement of the clinical condition of patients, normalizes blood pressure and its daily profile patients after 3 months of treatment, thereby enhancing their quality of life. Conclusions. L-arginine, as a pathogenically selected donator of nitric oxide, along with basic therapy of essential hypertension and COPD improved the state of the heart and vessels and should be used for treatment both diseases.