There is now good evidence that left atrial enlargement predicts cardiovascular outcomes. Moreover left atrial size is increasingly being recognized as a marker of atrial fibrillation recurrence following cardioversion and a predictor of radiofrequency catheter ablation efficiency in atrial fibrillation, now standard therapy in selected patients. Accordingly measurement of left atrial volume has gained clinical interest. In addition the diagnosis of left ventricular diastolic dysfunction relies in part on left atrial volume. Measurement of right atrial size is also clinically relevant and useful for the management of arrhythmias, pulmonary hypertension, valvular and congenital heart disease but less research and clinical data are available on the quantification of this cardiac chamber. Since a number of approaches can be used to measure left and right atrial size, it is important to know whether values obtained by different imaging modalities or by the same imaging modality using different measurement algorithms are interchangeable. This is particularly relevant for follow-up examinations. The most widely used and best available non invasive imaging technique for determination of atrial size is transthoracic echocardiography. The advent of real-time full-volume three-dimensional echocardiography allows rapid measurement of chamber volume without foreshortening of maximal dimension and without making geometric assumptions, as volume is reconstructed from endocardial contours of the entire chamber. Three-dimensional echocardiography is now frequently used for atrial volume quantification. Other three-dimensional imaging modalities like magnetic resonance imaging and computed tomography considered as non invasive reference methods for cardiac chamber volume determination are less available, more costly, more time consuming and have other specific limitations, and therefore are less suitable for atrial volume measurement in daily clinical practice. This review discusses the different non-invasive three-dimensional imaging modalities used for determination of left and right atrial size. It is intended to provide a critical review of available literature validating and comparing volumes obtained by different imaging modalities and measurement algorithms with special reference to investigations by the author in the field of three-dimensional echocardiography.