In an apparatus configured to acquire subject information, a light source is capable of generating light with a first wavelength and alight with a second wavelength different from the first wavelength, an acoustic wave detection unit detects a photoacoustic wave generated by illuminating a subject with light and output a resultant detection signal, and a signal processing unit acquires subject information based on a first detection signal output by the acoustic wave detection unit when the subject is illuminated with the light with the first wavelength and a second detection signal output by the acoustic wave detection unit when the subject is illuminated with the light with the second wavelength. An effective attenuation coefficient of the subject at the first wavelength is equal to an effective attenuation coefficient of the subject at the second wavelength.
