Atherosclerosis is the leading cause of morbidity and mortality in the Western World. Standard imaging techniques such as angiography, ultrasonography and computed tomography are still not effective in detecting atheromatous plaques in their early stages of development, when the lesions are most metabolically active and therapeutic interventions could beneficial. These techniques identify morphological changes such as increased wall thickness, decreased luminal diameter or related haemodynamic changes such as turbulence of blood flow. Unfortunately, all these phenomena occur when the plaque has evolved and encroaches on the lumen. There is a need for non-invasive methods that could assess the presence and the extension of atherosclerotic disease in its early stages, when the lesions are in their metabolically most active stage but still do not narrow the diameter of the lumen. Part I of this article presents an overview of the diagnostic procedures angiography, sonography, computed tomography and magnetic resonance tomography in imaging atherosclerotic lesions. Part II will concentrate on the diagnostic possibilities of scintigraphic imaging and positron emission tomography.