Is it normal to have one breast larger than the other after mastopexy with implants? (photo)

Congratulations on your recent surgery.  Mastopexy (breast lift) with implants is a great procedure for a patient wanting to replace volume and moving the areola up on the breast mound.  Symmetry is technically very difficult for a surgeon to obtain and your results looks great.  The breasts still need to heal and implants settle which can take several months.  As for the 20 cc difference, this is minor.  A shot glass holds 50 cc so 20 cc difference in the breasts would be very difficult to see. 

The difference between 440cc and 420cc is barely distinguishable as 200cc is frequently associated with one cup size difference.   A size discrepancy after breast augmentation is normal.  It is too early in the recovery process to make any final assessments.  The final results of your breast lift will appear over the next few months as breast shape and position continue to settle.  Incision lines will continue to fade over time. Kenneth Hughes, MD, Board Certified Plastic SurgeonLos Angeles, CA

It is common to compensate any size difference with a larger implant.  Based off of your picture it looks like you are pretty recent out of your surgery.  It will take time for your implants to settle to their final state. Keep an open dialogue with your surgeon to ensure that you remain happy with your results! 
Best of luck.    

You are early in recovery after breast lift with implants and asymmetry at this stage is very common.  Based on your history I would expect your symmetry to improve over the next 3 months.