BACKGROUND: Confusion remains over the definition of breakthrough cancer pain (BTcP) potentially leading to delayed diagnosis and treatment. METHODS: An on-line survey was conducted in four EU countries among relevant healthcare professionals and cancer patients diagnosed with BTcP. The roles of healthcare professionals (HCPs) were examined and their knowledge and use of available medications recorded. Patients were questioned on how BTcP affected their lives and on the medications they had received/were receiving. RESULTS: There was a 'time lag' of 58 and 13 weeks in Germany and Spain respectively between the initial diagnosis of BTcP and its treatment. Four in ten oncologists across the four countries considered themselves not fully confident in their choice of the appropriate therapy. A quarter of patients in Germany, Italy and Spain and four in ten in France were treated only with increased dosages of the therapy already prescribed for their background pain - often morphine. Almost another quarter received morphine in addition to their treatment for background pain. Oncologists indicated a need for faster-acting treatments revealing a potential lack of awareness of rapid onset oral opioids and patients expressed a desire for more effective pain relief and better psychological support. CONCLUSIONS: There is a need for a universal definition of BTcP to facilitate earlier and more accurate diagnosis. It is essential that BTcP is treated immediately on diagnosis with therapies that more closely mirror its temporal characteristics to ensure that patients' desire for more effective pain relief is fulfilled. SIGNIFICANCE: Many cancer patients suffered episodes of BTcP needlessly over many months due to missed diagnosis. Even after diagnosis, many physicians were not fully confident in their choice of 'rescue' therapy which perhaps is not surprising given the very low level of awareness of treatment guidelines, both national and international.