Adipose tissue is at a point of high interest in medical research, not only as an energy depot, but also because it secretes nearly more than 600 cytokines. These are termed‚ adipokines’. Human adipokines are involved in numerous metabolic processes, including the regulation of appetite, energy expenditure, insulin sensitivity, inflammation and cardiovascular activity. Thus, these could be clinically important as a markers of adipose tissue function and increased metabolic risk. The search for novel adipokines linking obesity to related co-morbidities has become a major topic in obesity research. In such work, there is an increasing need to define their function, their molecular targets and their potential clinical relevance as biomarkers or in the treatment of obesity and other metabolic diseases. Omentin (34 kDa) is a recently identified fat deposition-specific adipokine with multiple interactions. Concentrations of omentin have been shown to be decreased in patients with obesity and impaired glucose regulation, in patients afflicted with diabetes type 1 and 2, and in patients with polycystic ovary syndrome. These are all diseases commonly associated with insulin resistance and obesity. The aim of this study was to show and compare the latest information about omentin and its relationships with obesity, diabetes mellitus (DM), metabolic syndrome (MetS), inflammation, cardiac problems, sex hormone imbalances and cancer. The association of omentin with particular metabolic indexes may suggest that an elevation in omentin level may be seen as being a marker for leanness, while a decreased level will underline possible situations of overweight and obesity along with their comorbidities (diabetes, cardiovascular disease, metabolic syndrome, inflammation and even cancer). However, a challenge for the future is to fully understand the multiple role played by omentin. Thus, more studies in these matter are required.