The aim of this study was to compare data about the prevalence and proportions of the bacterial speciesAggregatibacter actinomycetemcomitans,Porphyromonas gingivalis, andParvimonas micrain periodontitis pocket samples collected from young, <35 years, and old, >35-year-old patients, YP and OP, respectively. The results from the analyses of a total of 3447 subgingival plaque samples analyzed for clinical diagnosis purposes by cultivation regarding the proportions of these species were collected from a database and elucidated. The prevalence of A.actinomycetemcomitanswas found to be more than twice as high (OR = 2.96, 95% CI; 2.50–3.50) in samples from the younger (42.2%) than the older group (20.4%) (p< 0.001). The prevalence ofP. micrawas significantly lower in samples from the younger age group (OR = 0.43, 95%) (p< 0.001), whereasP. gingivaliswas similarly distributed (OR = 0.78, 95%) in the two age groups (p= 0.006). A similar pattern was noticed forA. actinomycetemcomitansandP. gingivaliswhen high proportions (>50%) of the samples of these bacterial species were elucidated. In contrast, the proportion of samples containing >50% withP. micrawas lower compared with the two other bacterial species. Furthermore, it was noted that the proportion of samples from old patients containingA. actinomycetemcomitansin combination withP. micrawas almost three times higher than in samples whenP. micrawas replaced byP. gingivalis. In conclusion,A.actinomycetemcomitansshowed an increased presence and proportion in samples from young patients compared with the old patients, whileP. gingivaliswas similarly distributed in the two age groups.P. micrashowed an increased presence and proportion in samples from old patients compared with the young patients.