The paper presented the significance of EEG activation in diagnosing epilepsy in children and adolescents. EEG records of 108 patients between 3-19 years of age with the occurrence of various types of paroxysmal disorders who were admitted to Chair and Department of Developmental Neurology University of Medical Sciences in Poznań were analysed. Standard EEG was administered to all children twice: the first examination at rest with hyperventilation (HV) and photostimulation (FS) and the second one after total or partial sleep deprivation (DS). At awaking state normal records were stated in 57% of cases, in 15% paroxysmal changes in HV or FS appeared, in the rest of cases (28%) generalised paroxysmal disorders, localised changes, lateralised or diffused were noted. Among EEG activation methods DS occurred to be the most effective after it, 52 patients (48%) were diagnosed for generalised paroxysmal changes, 20% for localised, 3% lateralised and for 6% for diffused changes. Normal EEG were recorded in 22% of examined children and adolescents. The epilepsy were diagnosed in 59 (55%) of patients mostly with generalised seizures (28) partial secondarily generalised (16) and partially complex (11). In 49 (45%) children were diagnosed with other paroxysmal disorders.