This research focuses on the effects of an increasing pressure on the soot formation during combustion of vaporized liquid fuel. Therefore soot formation is measured in a laminar diffusion flame, with n-heptane as fuel, over a range of pressures from 1.0 to 3.0 bar. The soot volume fraction in the diffusion flames has been measured using Laser-Induced Incandescence (LII) calibrated by means of the Line Of Sight Attenuation (LOSA) technique. The values of the calibration factors between LII intensities and soot volume fraction from LOSA are slightly varied for different pressure. The integral soot volume fractions show power law dependence on pressures, being proportional to p(n), with n being 3.4 +/- 0.3 in the pressure range of 1.0-3.0 bar. (C) 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved.