The mass concentration and chemical composition, along with the size distribution of the aerosol, are key in determining its effects on health and the contribution of its sources. This study presents the aerosol size distribution in Bogotá, Colombia. The particulate matter (PM) samples were collected using an eight-stage cascade impactor, which simulates the deposition of particles in different fractions throughout the human respiratory system. The mean concentrations of PM9, PM2.1 and PM1.1 were 61.13 (± 27.7) and 30.21 (± 15.02) μg m-3, respectively, and the ratio of fine particles to inhalants (PM2.1 / PM9) was 0.5 . The aerosol mass size distribution was bimodal, with a coarse mode ranging from 4.4 to 5.4 μm and accumulation mode from 0.8 to 1.1 μm. Approximately 48% (± 5.1) of the PM mass could penetrate into the terminal bronchi and 27.2% (± 4.3) into the alveoli.