The Marmara region has been divided into six sub-regions having regard to the certain seismotectonic characteristics of the region, to study the seismicity. For this, the data belonging to both the historical and instrumental period has been used. The probabilities of earthquake recurrences were obtained by using Poisson statistical distribution models. Gutenberg-Richter (GR) relationship for each sub-region has been computed and, a-and b-values known as seismic hazard scaling parameters have been determined by linear least square (LLS) method and maximum likelihood (ML) method. The highest and the lowest b-values determined by LLS are found for sub-region 4 (Saros Gulf, 0.74 +/- 0.08) and sub-region 1 (Duzce, 0.56 +/- 0.06), respectively. The highest a-value for sub-region 4 as 5.05 +/- 0.05 and the lowest a- value for sub- region 3 (Tekirdag) as 4.12 +/- 0.02 are found. Likewise, the calculated lowest and highest b-values with ML are 0.55 +/- 0.05 for sub- region 1 and 0.68 +/- 0.07 for sub- region 4, respectively. Also, b-value for all region (108 years and M-S >= 4.0) are estimated as 0.71 +/- 0.03 with LLS and 0.65 +/- 0.02 with ML. The highest earthquake occurrence probabilities of M-S >= 7.0 in the next 100 years according to the Poisson distribution are found as 74.4% for sub- region 1 (Duzce), 58.6% for sub- region 2 (Izmit), 54.3% for sub- region 3 (Tekirdag) and 49.7% for sub- region 5 (Bandirma). The shortest recurrence period for the earthquake with the same magnitude is determined as 73 years for sub- region 1.