A: Pre-existing condition is an illness or medical condition for which you have taken treatment before the effective date of coverage of your new plan. Generally the insurance company will look back for 4months to 1 year but some conditions might demand entire lifetime too. Some pre-existing condition will be excluded from the coverage if it is not stable for a certain period of time. Before you go about finalisinga travel insurance plan that best suits you, its necessary to compare the coverage and definitions.