In this paper a multimodal optical resolution microscope in frequency domain is introduced. Fluorescence and photoacoustic signals are generated simultaneously using an amplitude modulated diode laser. The resulting signals are recorded by a lock-in amplifier. By scanning the sample, two-dimensional plots of the fluorescence and photoacoustic signals can be generated. In this paper, the signal-to-noise ratios of amplitude modulated signals are compared to those expected for pulsed excitation under the assumption that the maximum permissible exposure limits are fulfilled. Furthermore, it is described how to determine the excited state life-times from the measured frequency responses of the fluorescence or photoacoustic signals, respectively.