Summary: The prescription and usage of mucoactive drugs for inflammatory diseases of the respiratory system is increasing. This applies to both acute and recurrent infection of the respiratory tract and also chronic conditions like Chronic Obstructive Pulmonary Disease (COPD) and otitis with effusion (so-called glue ear). This development in clinical practice arises, at least in part, from a growing understanding of the fact that mucus hypersecretion with increased viscosity resulting in its impaired clearance is an important clinical feature of various respiratory disorders. The main purpose of mucoactive drug application is to reduce mucus viscosity and to enable its evacuation. S-carboxymethylcysteine (carbocisteine) is one of the most frequently prescribed mucoactive agents both for short-term treatment of acute respiratory tract infections such as bronchitis or sinusitis and long-term application as in conditions like chronic obstructive pulmonary disease (COPD), otitis media with effusion (“glue ear”) and also for other respiratory pathologies where problems with proper mucosal clearance occur. Carbocisteine possesses unique mucoregulatory activity. It normalizes the rheological properties of mucus by reducing the secretion of fucomucins and increasing that of sialomucins, making the sputum less dense and being effectively removed by ciliary transport. In addition to its mucoregulatory activity, carbocisteine exhibits free-radical scavenging and anti-inflammatory properties. Carbocisteine can be used as symptomatic medication in both lower and upper respiratory tract infections. It facilitates expectoration, significantly shortens the occurrence of ailments, including dyspnea resulting from persistent tiring productive cough. Carbocisteine is able to reduce the symptoms and exacerbations of chronic sinusitis and also reduces the likelihood of or delays drainage treatment in chronic post-infectious inflammation of the middle ear – otitis media with effusion. Long-term use of carbocisteine reduces the rate of exacerbations of COPD and improves quality of life. The well-documented activity of carbocisteine in COPD led this compound to achieve the B level of recommendation according to American and European recommendations.