What do you think, could mold illness show up on chest x-ray?

It depends...: It depends on what you mean by "mold illness." molds (a form of fungus), can cause many different diseases with varying symptoms. Some of these can be seen on a chest x-ray, but many will not. In general, the more symptomatic a patient is from a pulmonary standpoint (cough, chest pain, shortness of breath, etc) the more likely any possible pulmonary fungal infection will show up. I hope this helps.

Sometimes: Mold is fungus. Fungal infections can occur as densities on chest xray. Densities are reaction by immune system to infection. Immune compromised patients are more susceptible to these infections. Sometimes CT high resolution imaging of chest is performed to better define these lung densities. Usually fungal infections treated by appropriate antibiotics.