Financial planners have debated it for years, but from a pure dollars-and-cents perspective the correct answer is usually to pay your mortgage down first. Every time you make an extra mortgage payment you reduce the amount owed on the principal. If your mortgage interest rate is 5%, paying it off faster is like getting a guaranteed 5% return. Yes, you can get a better return than that in the stock market (if you’re lucky), but it’s not guaranteed. So unless you can find GICs that pay 5%, you may want to attack the mortgage first.