Misunderstandings due to terminology differences between health care providers and consumers may cause communication problems and adversely affect consumer access to health information, resulting in poor satisfaction for patients and providers. To investigate the usage patterns of consumer health vocabulary and evaluate controlled terminologies used in electronic medical records, we conducted a usability study of patient-friendly terms used in an ambulatory electronic medical record (EMR) and associated patient web portal. After identifying 340 unique diagnosis term/patient-friendly term pairs, we mapped the term pairs determined by UMLS to be pairs of synonyms, near-synonyms, or closely-related terms to the keywords of search queries extracted from a consumer health information web portal to learn the comparative frequency of use of members of each pair by consumers. We found out that use of patient-friendly terms could help to bridge the language gap between providers and consumers but not always. In some cases the professional diagnosis terms were used more frequently than their patient-friendly counterparts, typically in cases where the professional terms were more simple or common than the patient-friendly terms.