Mucus hypersecretion is a cardinal sign of both acute and chronic pulmonary diseases. Normally, mucus protects respiratory tract, but its overproduction leads to airway obstruction and promotes bacterial colonization. In the first part of our review we outlined the possible factors responsible for mucus hypersecretion and clinical consequences of this process. Mucolytic agents such as Ambroxol and N-acetylcysteine are able to alter the secretion of mucus and its physical properties which results in improvement of mucociliary clearance. Mechanisms of action and indications for use of mucolytics are presented. Mucolytics have been shown to have a role in improving lung functions and patients' quality of life. Undoubtedly they are useful as an adjunctive therapy of respiratory tract disorders.