Summary: Many drugs influencing mucous formation are utilized in treatment URTIs as well LRTIs. Among them a very interesting group is formed by thiol mucolytics. Their unique feature is a ‒SH group, responsible for depolymerization of mucous and anti-oxidative properties. Some of them e.g. acetylcysteine also may increase the antibiotics level in lower respiratory airway and affect the biofilm presence. Therefore, in this review we focused on thiol mucolytics and its importance in infection treatment.