Various methanofullerenes functionalized with either hydrophobic or polar groups have been synthesized. Studies of such compounds by surface pressure measurements and in situ UV-visible spectroscopy in Langmuir films show that these two types of functionalizations do not prevent the formation of aggregates at the nitrogen-water interface. Except for one compound studied in the present work, it appears that the aggregation occurs as soon as the spreading of the fullerenes solutions. However, the aggregates obtained appear to have different characteristics than those obtained with pure C-60.