Obstructive airway diseases, chronic obstructive pulmonary disease (COPD) and asthma have a high prevalence worldwide and constitute a considerable burden of disease. Although various treatments have evolved for these illnesses, they are often only partially effective in relieving symptoms and reducing underlying airway abnormalities. Inhaled bronchodilators and glucocorticosteroids have been the mainstay of therapy and no new classes of drug with effective anti-inflammatory activities have been introduced to clinical practice for almost 20 years. Recently, a new class of compounds, phosphodiesterase 4 inhibitors, have undergone development. This article will examine one such compound, roflumilast, which has recently shown promise as therapy for the principal obstructive lung diseases - COPD and asthma.