The objective of our work was to study the photobiomodulatory effects of low level laser therapy in addition to classic treatment of various periodontal diseases. Low level laser therapy is commonly used with good results in many medical domains, but the underlying mechanisms have not entirely been elucidated and ‘gold standard’ optimum working protocols have not yet been established in dentistry. The laser beam parameters and the application techniques are very important, as the clinical results depend entirely upon them. The bleeding time, pain relief time, and the bone recovery time in the treatment of periodontal disease were measured, and other non-quantifiable results (e.g. reduction of inflammation and oedema) were followed in two groups: the control group who underwent classic treatment of periodontal diseases, and the experimental group where LLLT was applied in addition to the classic treatment. In all cases, the measured parameters were less severe or shorter for the experimental group then for the control group. Very good results were obtained for the patients suffering from diabetes. In conclusion, in all cases, LLLT as adjunctive therapy to classical treatment led to better results in the treatment of periodontal diseases, but the results also depended upon the age and general health of the patients, and existence of any metabolic problems.