Droplet breakup/disintegration is a common phenomenon in a variety of scientific and engineering applications. During its breakup (which is also known as secondary breakup), the droplet deforms and breaks into smaller droplets. Studying droplet deformation is important as it is the first stage which the droplet goes through during its breakup. It has been shown that droplet deformation significantly affects the drag acting on the droplet which in turn affects droplet-gas relative velocity, droplet breakup and coalescence process and drop size distribution in a spray. The liquid properties which play a crucial role in droplet deformation are surface tension, viscosity and density. In the present study, the effect of these properties on the droplet deformation behaviour is investigated by choosing test liquids carefully. The test liquids are chosen and grouped such that only one of the three properties differs significantly from liquid to liquid in a group, while the other two remain nearly the same. Hence, the effect of each of these properties (surface tension, viscosity and density) on the droplet deformation behaviour can be identified.