She is a Board Certified Lactation Consultant, as well as a retired La Leche League Leader. There appears to be no correlation at all between breast size and milk production.
Larger breasts have a higher proportion of fatty tissue, compared to glandular tissue.
This of course has no effect on the amount of milk you are able to produce. Women with very small breasts may worry that they will not be able to properly nourish their baby, but it is very rare for a woman to be born with insufficient glandular tissue. Interestingly enough, women with small breasts may find they have less difficulties breastfeeding than nursing moms with larger breasts. Proper positioning, which is so important when breastfeeding, may present special challenges for the large breasted nursing mother. One man's uncensored memoir of pregnancy.