Maureen,
Being a dive shop owner I used to sell alot of Cressi-Sub Big Eyes Masks. It is a great mask but for new divers it sometimes leaks alot on them and this is why. The skirt on this mask is not that big so if you have a small face and smile it will leak. So before taking it out diving put it on as if you were trying it for the first time and smile a little. If it does not fall off your face you may be ok. Also, if it does not fall off put the mask on with a regulator in your mouth and then smile a little if it does not fall off great, if it does try another mask or you will need to re-adjust your smiling habits.
Hope this helps somewhat. If you ever have any other questions or need any equipment give me a call or e-mail me.
Thanks
John
SCUBA "U"
708-599-2630