A complete reliable methodology including several extraction and chromatographic techniques has been developed for the determination of selected organic compounds in atmospheric aerosol particles. Size separated ultrafine particles (Dp ≤ 50nm) and total suspended particles (TSP) were collected in a urban and forest environment. One third of the samples contained TS particles and the rest of the samples were size-separated (30, 40 or 50 nm particles) with a differential mobility analyzer (DMA). Gas chromatography-mass spectrometric and liquid chromatography-mass spectrometric methods were developed for the analysis of the target compounds and the sample pretreatment was shortened by exploiting ultrasonic energy. The investigated compounds included seven amines (average concentrations ranged between 0.1 and 10.9 ng m⁻³), eight aldehydes (0.1–11.9 ng m⁻³), two polyols (0.1–81.5 ng m⁻³) and sixteen acids (0.1–47.2 ng m⁻³). The whole methodology including sample preparation and analysis methods was carefully validated by comparison of the results obtained with those provided by a conventional extraction method, non-assisted by ultrasound and by standard addition methodology, respectively. There were clear differences, up to two orders of magnitude, in the concentrations of the target compounds in aerosol samples with different sizes collected from an urban and forest environment.