In this chapter, we elaborated on the two main forms of distorted symptom reporting: symptom over- and underreporting. In certain situations, individuals might exaggerate their symptoms. For instance, defendants facing legal issues may overstate their mental health problems. This type of behavior is often described with terms such as "faking bad," "feigning," and "malingering," though these should not be used interchangeably with symptom overreporting, as each term carries distinct connotations. Conversely, in other scenarios, individuals may underreport their symptoms. For example, a parent involved in a custody dispute might minimize genuine psychological issues. Symptom underreporting differs from "faking good" or "superlative self-presentation". Symptom validity tests serve as valuable tools for clinicians and experts to identify distorted symptom reporting in patients, defendants, or plaintiffs. There are numerous symptom validity tests, each varying in diagnostic efficacy, often quantified by Likelihood Ratios. Deviant scores on these tests suggest either over- or underreporting, particularly when the Likelihood Ratio is high. Relying solely on subjective clinical impressions to detect over- or underreporting is not advisable, as it may result in missed cases and misclassification of individuals with genuine issues (i.e., false positives). Therefore, incorporating symptom validity tests into assessments, especially when results can be discussed with the individuals being tested, proves beneficial in correcting distorted symptom presentations. However, these tests alone do not provide sufficient information regarding the motivation underlying symptom over- or underreporting; thus, additional contextual information is necessary.