In this study the durations of the averaged P-wave signal were compared by using different filter techniques (unidirectional-, bidirectional-, Fir- and Lsq-filter) in order to differentiate between a group of patients with paroxysmal atrial fibrillation and a control group with healthy volunteers. 50 healthy patients (mean age 29.8 years) and 56 subjects (mean age 60.9 years) with paroxysmal atrial fibrillation were examined, where a significant difference (p < 0.5) of the mean P-wave signal was observed for all filter techniques. A P-wave duration threshold of 110.0 ms (upper limit) for the bidirectional-filter with a sensitivity and specificity of 84 % showed the best results in differentiating between the two groups. The unidirectional-filter reaches a sensitivity and a specificity of 61 % with an upper limit of 138.5 ms. The upper limit of the Fir-filter turned out to be 121.0 ms with a sensitivity and specificity of 79%. The Lsq-filter has an upper limit of 122.0 ms and a sensitivity and specificity of 67%.