Inhalation therapies are central to the management of chronic obstructive pulmonary disease (COPD). Although, findings from previous studies reveal suboptimal use and a wide range of problems with inhaler handling among COPD patients, very little is known about how and why problems arise. A systematic search of studies related to the topic area was conducted using Scopus and PubMed, from 2000 to 2013. As a result, twenty-two studies were included. Most studies had similar baseline characteristics. This review indicated that adherence to inhalation therapy was of concern. Rates of non-adherence to medication ranged from 29.5% to 80%. This review confirms non-adherence as a problem among patients and identifies factors which were potential contributors to medication non-adherence. The review reveals issues in operating the inhalation devices especially with the pressurised metered dose inhalers (pMDIs), which may lead to sub-optimal therapeutic outcomes and treatment failures.