We report the observation of midinfrared intersubband (ISB) absorption in nearly lattice-matched AlInN/GaN multiple-quantum-wells. A clear absorption peak is observed around 3 mu m involving transitions from the conduction band ground state to the first excited state. In addition to ISB absorption, photoluminescence experiments were carried out on lattice- matched AlInN/GaN single quantum wells in order to determine the spontaneous polarization discontinuity between GaN and Al0.82In0.18N compounds. The experimental value is in good agreement with theoretical predictions. Our results demonstrate that the AlInN/GaN system is very promising to achieve crack-free and low dislocation density structures dedicated to intersubband devices in the 2-4 mu m wavelength range.