Can anyone tell me what determines primary coverage? In 2010, my 21 year old son had COBRA insurance, through my husband's employer. While trying to determine if we would keep the coverage or buy private insurance, we decided to buy the private insurance, but also paid for the COBRA insurance. Thank goodness we did, because he had to be hospitalized, and has been diagnosed with a serious mental condition. When purchasing the private insurance, we did not think to ask if it had mental coverage, and later found out that it did not. He had no previous history of a mental condition, just a normal kid, who's mostly been to the doctor for check-ups. The COBRA insurance has covered the bills for the hospitalization at the mental hospital. Now that the laws have been changed in 2011, he is back on my husband's insurance and we have kept the private insurance, also. My question is ..... if he goes to the doctor for something medical (not mental), who is considered the primary insurance? Also, I worry that he will have problems getting insuance in the future, after he can no longer have insurance through my husband, because he will have a pre-existing condition. I think he can stay on my husband's insurance until age 26. Any advice would be appreciated. This has really thrown us for a loop.