Generally, if you carry balances on your credit cards, canceling one of the accounts will hurt your FICO score.  One key factor in the FICO calculation is the debt utilization ratio, which shows how much of your available credit you are actually using.  If the total of the limits on all your cards adds up to $20,000, and your balances add up to $10,000, you have a utilization of 50%.  That doesn't sound too bad, right?  Actually, that is relatively high in the eyes of the FICO calculation.  You should try to keep utilization low, below 30% if possible.  Zero percent utilization is best, of course, because creditors love most to loan money to people who appear not to really need it!