With the increasing importance of early type 2 diabetes (DM2) and obesity detection, it is useful to reevaluate leptin role in these conditions. Our study aimed at investigating circulating leptin concentrations in a group of patients with DM2, and at assessing in detail whether leptin concentrations correlate with selected biochemical, clinical parameters and markers of systemic inflammation in patients with DM2 and in healthy volunteers. In our work, we analysed samples and data drawn from 71 patients aged 61.4 ± 11.7 years, who have been diagnosed with type 2 diabetes, as well as from a healthy control group (HC) consisting of 51 healthy subjects with a mean age of 57.8 ± 13.7 years. Therein, the concentration of leptin in the DM2 patients was significantly higher than in the HC (p < 0.01), with median value of 16.59 (IQR 8.58-33.39) ng/ml in the DM2, vs median value of 6.66 (IQR 4.52-21.40) ng/ml in the HC. In the analysis of variance, higher leptin concentrations were revealed in the DM2 group as compared to the HC, and this figure remained significant after adjusting for gender and age (p < 0.001). Moreover, it was independent of HOMA-IR (p = 0.003). However, the differences in leptin levels between the groups disappeared when additional adjustments for anthropometric parameters (BMI, waist circumference) were applied (p = 0.088). Beyond the aforementioned, significant positive correlations were found in the DM 2 group between leptin level and CRP (r=0.256; p < 0.05) and IL-6 (r = 0.345; p < 0.01). Among the selected variables, only gender and BMI were included in the predictive model explaining the variability of leptin, and, in total, were responsible for 72.6% of the original variation of the studied adipocytokine. The results of this study have led to conclusion that leptin may participate in the complex pathogenesis of DM2 and be a predictor of the development of this disease. As higher concentrations of leptin coexist with obesity, and this situation correlates positively with markers of inflammation (CRP, IL-6), leptin level, hence, should be considered in the pathogenesis of DM2.