It is generally accepted that cAMP regulates Ca²⁺-dependent exocytosis in many secretory cells but the precise molecular mechanism of this phenomenon remains unexplained. Two separate cAMP-modulated pathways were described to control Ca²⁺-dependent exocytosis, through either PKA or Epac2. The aim of our study was to characterize the role of these two cAMP-dependent pathways on the kinetics of regulated exocytosis in mouse pancreatic beta-cells. The effects on different exocytotic components were studied using whole-cell patch-clamp based capacitance measurements (C_m). Exocytotic activity was stimulated using slow photo-release of Ca²⁺ bound to NP-EGTA producing a ramp-like increase in cytosolic Ca²⁺ [Ca²⁺]_i. In control cells when [Ca²⁺]_i reached threshold level, typically a biphasic increase in C_m has been triggered. The first phase of C_m change (exocytotic burst) reached its maximal amplitude within the first second (amp1) and the second phase reaching maximal amplitude (amp2) within approximately next 5 seconds. In addition, we observed that the Ca²⁺-dependency of the rate of the C_m follows the saturation kinetics with high cooperativity and half-maximal rate of the C_m change (EC₅₀) at 2.6 ± 0.2 mM. To assess the effect of cAMP we first performed the intracellular washout of ATP that should result in reduced cAMP production. This manipulation pushed the Ca²⁺-dependency of the first C_m phase towards higher [Ca²⁺]_i but did not influence the C_m amplitude. On the other hand the amplitude of the second phase was strongly reduced. In the following experiments, we clamped the cytosol at saturating 200 mM cAMP. This manipulation pushed the Ca²⁺-dependency of the exocytotic burst to significantly lower [Ca²⁺]_i in comparison to the controls, while again there were no differences in the amplitudes of C_m change. To address the question, whether cAMP acts through PKA- or Epac2-sensitive mechanism we included 100 mM 6-Phe-cAMP (selective PKA agonist), 500 mM Rp-cAMPs (a competitive antagonist of cAMP-binding to PKA) and 100 mM 8-pCPT-2'-Me-cAMP (specific Epac activator) 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 ± 0.1 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 primary beta-cells mainly through PKA-dependent mechanism by sensitizing the insulin releasing machinery to [Ca²⁺]_i.