We report the growth of vertically aligned single-wall and multi-wall carbon nanotube forest using a Laser Activated – Catalytic Chemical Vapor Deposition process. The experiments were performed in a cold-wall reactor filled with an ethylene-hydrogen-argon gas mixture in a 5:2:8 ratio at ambient pressure. A near infrared continuous wave laser diode was focused on a flat specimen to promote a local carbon nanotubes growth. Si substrates coated with a 20 nm Al2O3 layer on which a 2 nm thick Fe film was deposited were used. Growth products are characterized using Raman spectroscopy and Scanning Electron Microscopy. In this paper, we specifically discuss the influence of the laser exposure time on the growth process.