Endothelial dysfunction plays an important role in the pathogenesis of many common diseases, like atherosclerosis and hypertension. The key role of the interaction between oxidative stress and inflammation in causal mechanisms of these diseases is widely accepted. Until recently, perivascular adipose tissue was not taken into account while looking at mechanisms of these disorders. However, it has recently been demonstrated that most processes involved in endothelial dysfunction development are taking place in this tissue. Adipocytes are an important source of free radicals and pro-inflammatory cytokines. These molecules lead to further enhancement of oxidative stress, through uncoupling of endothelial nitric oxide synthase (eNOS) and production of peroxynitrite radical instead of nitric oxide which further disrupts eNOS function. In addition, macrophages and T lymphocytes infiltrate adipose tissue as a result of chemotactic proteins release, upon oxidative stress activation, which further enhances inflammation. Thus, the chronic inflammation, which develops in this compartment of adipose tissue in patients with obesity, is the first step in the development of atherosclerotic plaque or hypertension. That is why comprehensive understanding of ongoing processes within perivascular adipocytes is so important.