The quantitative characterization of sooting flames in terms of soot load and total soot surface area continues to be a major challenge in both fundamental investigations and practical applications. More particularly, a major interest can be found to discriminate the two classes of particulate, namely soot and cenosphere, presents in power generation plants fuelled with heavy fuel oils. The Laser-Induced Incandescence (LII) technique is widely employed for the determination of soot volume fraction but LII may also be used to derive the particle diameter, profiting from the size-dependent cooling behavior of the laser-heated particles. The temporally resolved LII emissions has been successfully used in a heavy fuel oil spray flame to distinguish the two classes of carbonaceous particles produced during the heavy fuel oil combustion. Moreover, it has been possible to follow along the flame axis the formation and burn-out of these two classes of particulate and their relative amount in terms of volume fraction.