The CMU is the compulsory cross-border health insurance offered by France, unlike LAMal which is the Swiss compulsory health insurance.
The CMU offers coverage similar to that of the French Social Security system, so expensive treatments such as hospitalization is only minimally reimbursed. This coverage reimburses medical expenses incurred in France, however, medical care in Switzerland is not reimbursed, or only under certain specific conditions or in emergency situations.
The LAMal covers health costs both in France and in Switzerland. Its coverage is somewhat more complete, but dental and optical expenses are also poorly reimbursed.
Making the right choice between these two schemes is all the more important as some border regions such as Ain are described as a medical desert. Having access to healthcare in Switzerland may therefore be essential for some border workers.