Several systemic and cardiac diseases cause an impairment of left ventricular filling or of the ability to maintain cardiac output, without an increase in end-diastolic pressure. Prevalence of diastolic dysfunction has been found to be higher than systolic dysfunction in most studies. Many physiological conditions (age, sex and body weight), and pathological processes, such as cardiac or systemic diseases, can increase the incidence of diastolic dysfunction. Early diagnosis of left ventricular diastolic impairment has been demonstrated to have important therapeutic implications. Several invasive or non-invasive methods to investigate diastolic properties of the left ventricle have been described; a large number of studies compared different parameters of diastolic function in order to find the most accurate: this is of particular prognostic relevance since diastolic dysfunction may remain asymptomatic for a long period before resulting in overt heart failure. The purpose of this article is to provide an extensive review of the contemporary literature regarding diastolic function assessment and its role in daily practice.