cAMP is an important second messenger with a plethora of cellular effects and biological roles. To monitor and visualize cAMP in intact living cells, electrophysiological and fluorescent methods have been developed based on activation of all three types of cAMP effectors: protein kinase A, cyclic nucleotide-gated channels, and exchange protein directly activated by cAMP. In this review, we describe and compare these techniques in terms of their robustness, sensitivity and spatio-temporal resolution.