Despite increased interest in treatment of senior cancer patients, older patients are much too often undertreated. This review aims to present data on treatment practices of older women with breast and gynecologic cancers and on the consequences of undertreatment on patient outcome. We also discuss the reasons and validity of suboptimal care in older patients. Numerous studies have reported suboptimal treatment in older breast and gynecologic cancer patients. Undertreatment displays multiple aspects: from lowered doses of adjuvant chemotherapy to total therapeutic abstention. Undertreatment also concerns palliative care, treatment of pain, and reconstruction. Only few studies have evaluated the consequences of nonstandard approaches on cancer-specific mortality, taking into account other prognostic factors and comorbidities. These studies clearly showed that undertreatment increased disease-specific mortality for breast and ovarian cancers. For other gynecological cancers, data were insufficient to draw conclusions. Objective reasons at the origin of undertreatment were, notably, higher prevalence of comorbidity, lowered life expectancy, absence of data on treatment efficacy in clinical trials, and increased adverse effects of treatment. More subjective reasons were putative lowered benefits of treatment, less aggressive cancers, social marginalization, and physician's beliefs. Undertreatment in older cancer patients is a well-documented phenomenon responsible for preventable cancer deaths. Treatments are still influenced by unclear standards and have to be adapted to the older patient's general health status, but should also offer the best chance of cure.