Unlike child support payments, alimony payments are considered to be taxable income. If you received alimony (or "separate maintenance") at any time during the tax year, you must report the full amount received as income, and it will be added to your AGI. Any child support amount you received, even if it was collected in conjunction with alimony or maintenance payments, is non-taxable, and should not be reported.
Be aware that the party paying alimony is expected to report both the full amount paid during the year and the social security number or tax ID number of the recipient. In fact, alimony paid can be taken as a tax deduction, so it is unlikely that it will not be reported in full. If you fail to report your receipt of these payments, or you report receiving less than your ex-spouse actually paid, you are letting yourself in for an audit and tax penalties.
If you paid alimony or maintenance to your ex, you will be able to take a deduction for these payments in most cases. You are not eligible for the deduction if you file a joint return with the party receiving alimony. You may also not be a member of the same household while making the payments.