Display omitted •The difference in attachment between particles and air/oily bubbles was quantified.•The wetting film between hydrophobic particles and oily bubbles was more susceptible to rupture.•The formed TPCL when the hydrophobic particles adhered to oily bubbles was larger than that when they adhere to air bubbles.•The oily bubble had both strong collecting power and excellent selectivity for hydrophobic particles. The attachment between particles and bubbles is a very important basic unit for mineral flotation. In the present study, methylation processing for glass spheres with trimethylchlorosilane was used to prepare particles with different surface hydrophobicity, and a visualization setup was assembled based on high-speed camera technology to investigate the dynamic attachment process of particles onto air/oily bubbles. More importantly, the difference in the attachment process between particles and air/oily bubbles was successfully quantified with the software Image Pro Plus 6.0. It was found that the wetting film ruptured at about 36 ms during the attachment between the hydrophobic glass sphere M2 and air bubbles, while it occurred at about 28 ms during the attachment between M2 and oily bubbles. Moreover, the formed three-phase contact line between hydrophobic particles and oily bubbles was larger than that between hydrophobic particles and air bubbles, suggesting a more stable attachment of the former. In contrast, no successful attachment of the hydrophilic glass sphere M0 onto air or oily bubbles was observed. These findings strongly demonstrated that oily bubbles had both strong collecting power and excellent selectivity for hydrophobic particles in flotation. This study improved the understanding of the difference between oily-bubble and conventional flotations.