Surgical excision is still the best option in attempting to cure many solid cancers. Even patients with tumours that have already metastasised to regional lymph nodes or to distant sites are potential candidates for surgery [1]. With this in mind, accurate staging of the disease and detection of all cancer sites are of the utmost importance in order to allow selection of those patients who may really benefit from complete surgical resection. Several imaging modalities are currently used to preoperatively assess cancer patients. Among them, over the past decade functional imaging with positron emission tomography (PET) has emerged from being primarily a research tool to become a valuable non-invasive technique which is now playing an increasingly important role in the diagnosis and staging of malignant disease, treatment monitoring and therapy planning. In particular, PET with the labelled glucose analogue F-fluorodeoxyglucose (FDG) has become an established modality for cancer imaging. However, this technique is not perfect: small lesions and those adjacent to sites of high physiological FDG uptake can be missed; moreover, false-positive results due to benign diseases are possible [2]. The introduction into clinical practice of hybrid PET/computed tomography (CT) scanners has solved some of these problems: fused PET/CT imaging allows accurate anatomical localisation of functional abnormalities and reduces the incidence of falsepositive findings by facilitating the differentiation of normal physiological uptake from pathological uptake. Many recently published studies have demonstrated that, in several clinical applications, PET/CT imaging consistently outperforms PET and CT imaging carried out separately and analysed together [3]. Nevertheless, the suboptimal spatial resolution of PET still limits the accuracy of PET/CT in characterising lesions ≤5 mm. It is intuitively expected that the availability of a PETsensitive probe able to intra-operatively identify all FDGavid tumours may improve preoperative PET staging because the detection system of such a device can be placed close to the radiation source [1]. Intra-operative probes have become important devices in nuclear medicine, especially the gamma probes which detect gamma photons from single-photon emitters like Tc and In [4, 5]. In fact, in addition to the inspection and palpation traditionally used by the surgeon, intra-operative detection of radiopharmaceuticals by hand-held gamma probes is increasingly been performed. The main clinical applications of radioguided surgery are sentinel lymph node mapping for several kinds of tumour and detection of parathyroid adenoma [6]. The use of an intra-operative probe during surgical oncology, after the administration to the patient of a radiopharmaceutical that accumulates in the tumour, can help the surgeon in finding the neoplastic lesions. Moreover, by means of the probe, the surgeon can also confirm that the excised parts really do contain cancer tissue, and that the tumour has been completely removed. In this application, the positron emitter FDG can be detected by two methods: detection of the beta particles or detection of the annihilation gamma photons. In this issue of the European Journal of Nuclear Medicine and Molecular Imaging, Piert and colleagues [7] report the results of a beta and gamma probe system for the intra-operative localisation of tumour sites in 17 patients Eur J Nucl Med Mol Imaging (2007) 34:1530–1533 DOI 10.1007/s00259-007-0482-6