This paper examines the on- and off-line identity performance of a group of Hong Kong middle-class working mothers who are users of an internet based community. The development of my involvement in this community from lurker to participant and then to virtual ethnographer provides a unique opportunity to compare the on- and off-line interactions of an Internet based community. By examining the relationship between the dominant discourse of motherhood and these women's motherhood performances on- and off-line, three modes of performativity are identified and discussed. I argue that although there is considerable pressure within this community to uphold the dominant motherhood discourse, users' reflexivity and subversion regarding this performance are evident in both on- line and off-line contexts. In particular, users' performativity in what I call the 'Si Nais behaving badly' mode can be read as a reaction towards, though not necessarily subversive of, society's prevailing conception of motherhood. My findings throw light on how the structure of internet chat frames these women's presentation of self, and how internet chat exposes aspects of their self-hood, which portray a much more varied identity than the literature on motherhood currently suggests.