Psychogenic nonepileptic seizures (PNES) are paroxysmal events superficially resembling epileptic seizures. Although exploring the subjective experience is key in the management and care of patients with epilepsy or PNES, there is a lack of research into the subjective symptomologies. The primary aim of this thesis was to investigate the phenomenology and clinical implications (diagnostic, prognostic and therapeutic) of the lived experience of epilepsy or PNES. Firstly, a systematic synthesis of 21 qualitative studies investigating personal experiences of PNES was conducted. Five key themes emerged revealing experiences of treatment, impact to daily life, and emotional events, as well as differences between the seizure accounts of those with epilepsy. The first empirical study in this thesis explored a series of self-reported measures demonstrating that, subjective experiences could contribute to the diagnostic process as symptoms of panic associated with episodes of transient loss of consciousness could be used to distinguish between PNES and epilepsy or syncope. In study two, a series of multiple-regression analyses revealed that in both epilepsy and PNES, illness perception was a stronger predictor of health-related quality of life (HRQoL) when compared to demographic and condition-related factors. In study three, it was found that writing about experiences of living with a seizure disorder was associated with qualitative and quantitative benefits, including improved HRQoL one-month later. In the final series of studies, it was demonstrated that analysing and comparing individuals’ written accounts of PNES or epilepsy could help to improve our understanding towards some of the problems that individuals experience, as well as highlight clinical implications. In conclusion, research into the subjective experience of seizure disorders is a valuable area of research. More specifically, in-depth investigations are needed into the impact, prevalence and management of specific experiences, which include the voices of individuals that so far have been under-represented.