During the past two decades, the importance of the quality of low-density lipoprotein (LDL) particles – in addition to its quantity – has become of increasing interest. The risk of cardiovascular events was recognized to be closely linked to a predominance of small, dense LDL particles. In addition, in patients with Type 2 diabetes mellitus, the disease itself and its severity (in particular the degree of insulin resistance) is associated with this subclass of LDL particles. Lipid lowering as well as antihyperglycemic drugs have been evaluated in many studies concerning their effect on LDL particle size. It has increasingly been recognized that a reduction of LDL quantity is not necessarily associated with a beneficial effect on LDL quality. Advances in the understanding of alterations in LDL quality may therefore influence the choice of the therapeutic regimen in patients with diabetes in the future.