To clarify the relationship between the structure and the ability of fluorinated AOT analogues for W/scCO(2) microemulsion formation, we examined the AOT analogues having fluoroalkyl groups of different lengths, and CF2H, CF3, or CF(CF3)(2) moieties at the terminal of the fluorinated CO2-philic tails. It was found that both the length and the structure of the fluoroalkyl groups contained in AOT molecules affect the ability.