The influence of the growth parameters on the photoluminescence (PL) spectra has been investigated for samples with columnar morphology, either with InN columns on original substrates or as free-standing nanowires. Valuable information about band gap and electron concentration was obtained by line shape analysis. Optical band gaps between 730 and 750 meV and electron concentrations of 8 × 1017 to 6 × 1018 cm-3 were derived from the fit of the PL spectra of different samples. The crystalline quality of the wires was investigated by high-resolution transmission electron microscopy.