Cyclic AMP regulates Ca²⁺ -dependent exocytosis in many secretory cells through a protein kinase A (PKA)-dependent or cAMP-GEF/Epac-dependent pathway. We characterized the role of these two cAMP-dependent pathways on the kinetics of regulated exocytosis in mouse pancreatic beta cells. The whole cell patch clamp was used simultaneously with slow photo release of caged Ca²⁺ to elicit membrane capacitance change (C_m). In most of the control cells the C_m increase is biphasic with the first phase (exocytotic burst with maximal amplitude - amp1) and the second phase of C_m change (amp2). We observed that the Ca²⁺ -dependency of the rate of the C_m change follows the saturation kinetics with high cooperativity and half-maximal value (EC50) at 2.6 ±0.2 mM. To asses the effect of cAMP we first performed the intracellular washout of ATP that should result in reduced cAMP production. This manipulation did not influence the amp1 while the amp2 was strongly reduced. Next we clamped the cytosol at saturating 200 mM cAMP. This manipulation pushed the Ca²⁺ -dependency of the exocytotic burst to significantly lower [Ca²⁺]_i (1.5 ±0.2 mM of free Ca²⁺). To address the question whether cAMP acts through PKA- or Epac2-sensitive mechanism we included 100 mM 6-Phe-cAMP, 500 mM Rp-cAMPs and 100 mM 8-pCPT-2'-O-Me-cAMP into the pipette solution. PKA activation or inhibition in primary beta cells significantly shifted the EC50 of the exocytotic burst in the opposite directions (1.6 ±0.3 mM and 3.0 ±0.1 mM in cells treated with 6-Phe-cAMP and Rp-cAMPs, respectively), while specific activation of Epac2 did not change the Ca²⁺ sensitivity. Our findings suggest that cAMP modulates the rate of exocytosis in pancreatic beta cells mainly through PKA-dependent mechanism by sensitizing the insulin releasing machinery to [Ca²⁺]_i.