A mod will take your existing loan and make changes to it it can lower your interest rate and your payment or just lower your payment the bank will take your financial information from you and then they will determine how much you can afford to pay a month then the mortgage company will make a decision based on the information they have got from you if they will do the mod but with the new obama plan they will give you a mod for 3 months to see if you can make the new payments is you can then you get the mod if you can’t then you don’t and the obama plan will give you a fixed interest rate instead of an adjustable one
A refinance will give you a completely new loan so you could get a lower interest rate and a new payment but if you are behind in your current mortgage most banks will not touch your loan and you will have to try and get a modification

Home loan modification is modifying the existing terms and conditions of your current mortgage. Usually a fee is required upfront. It usually takes about 90 days. On average this fee amounts to about 3000 dollars. Usually a modification is done only when you present a significant risk to the lender, such as upside down mortgage, loss of job, illness, or a drastic increase in rate or payment usually you are behind in your payments. No credit check is required.

Mortgage refinancing is selling your existing mortgage note to another lender by increasing the loan amount to cover the costs associated with the refinance. Usually this ends up costing you more money than a mortgage modification about 3000 dollars for every 100000 dollars financed. You need good credit to refinance.