There remains a discord among orthodontists regarding the usefulness of a lateral cephalogram radiograph as a part of diagnostic records for treatment planning. Today, orthodontists take diagnostic lateral cephalograms largely based on a personal preference, rather than following any evidence-based approached for determining whether taking the radiograph will affect treatment planning. The aim of this study is to identify patients with the type of malocclusion for which the availability of a lateral cephalogram radiograph will affect the treatment plan. This would prevent patients, whose treatment plan would not benefit from a diagnostic lateral cephalogram, from receiving unnecessary ionizing radiation. The data for this study was obtained from responses to two questionnaires, mailed five weeks apart, to ten orthodontists with clinical experience. Primarily, the orthodontists were required to treatment plan twenty cases, twice, once with full diagnostic records including a lateral cephalogram radiograph and once without. Six orthodontists completed both questionnaires. Based on the data, it was found that for approximately 25% of patients having a lateral cephalogram radiograph does affect treatment planning. These patients present with bilateral, sagittal dental malocclusions, matching significant soft-tissue profile disharmony and at least one arch with a moderate arch length discrepancy. A larger, follow-up study is suggested to further investigate the relationship between malocclusion, lateral cephalogram radiographs, and treatment planning.