Children are familiar with situations in which air resistance plays an important role, such as parachuting. However, it is not known whether they have any understanding about the concept of air resistance, how air resistance affects falling objects, and the differential effect it has on different objects. The literature reveals that there are misconceptions even among undergraduate physics students about how air resistance is affected by the mass and size of falling objects. A study was carried out in Hong Kong to explore Grade 6 students' (aged 11-12) conceptions of air resistance with respect to falling objects of different size and mass, and whether the subjects showed any change in their conceptual understanding after participating in an egg-dropping race. The findings show that students had a wide range of conceptions, which could be characterized into different levels. Their conceptions seem rather robust, and more structured interventions are required to bring about changes in students' conceptual understanding of air resistance. (Contains 4 tables and 2 figures.)