Objectives: Permanent teeth impaction is a common clinical occurrence in the orthodontic offices (16.7%). However, impaction of 1st & 2nd Molars is rare. Delayed development and eruption of 1st permanent molars appears in most cases in the upper jaw. Nevertheless, there is a report in literature describing very low prevalence of lower first molar impaction. Sometimes first molar impaction is associated with Primary failure of eruption: a failure in eruption mechanism of the teeth. In these cases teeth don't respond to orthodontic forces, therefore orthodontic treatment in these cases is futile. Impaction of second permanent molars is also very exceptional by incidence (0.003%), associated mainly with arch length deficiency, unilateral in most cases and occurs more in the lower jaw. Treatment accompanied by number of difficulties, involved with long and unpredictable treatment. Hence orthodontist faces the inherent dilemma either to treat or to extract the teeth. Methods: A series of clinical cases demonstrate the diagnosis difficulties, treatment plan including few of the possible treatment modalities, treatment result including retention period.Results: Careful treatment planning and treatment re-evaluation during active treatment are significant factors in the aim to achieve higher rates of success. Treatment options are various with some common principles: gaining adequate space, surgically exposure of impacted tooth, anchorage reinforcement, orthodontic traction – distally directed forces, intermaxillary versus intermaxillary forces. Duration of treatment is long and patient's cooperation and motivation are essential.Conclusions: Impacted permanent first and second mandibular molars present the orthodontist with a challenge regarding diagnosis and treatment modalities.