We present a magnetic study of palaeohearths within Lazaret cave (Nice, France) that demonstrates how to recognize fired structures in similar geological contexts. Using magnetic field and susceptibility mapping, excavated and potentially still-buried palaeohearths of the cave are investigated. Our study reveals some difficulties in conducting a magnetic field survey to detect combustion features in a cave due to noise and ambiguities in anomaly assignment. To overcome these difficulties, discrete measurements and a specific post-processing methodology were applied to remove the magnetic noise generated by surrounding artificial sources. In addition, experimental and numerical modelling constrained by laboratory examinations of the magnetic mineralogy were performed to better identify the magnetic imprint of such fireplaces. We confirm that a short-term fireplace produces a thin ash-bearing layer characterized by a high magnetic susceptibility and a high frequency dependence due to a large proportion of grains of pseudo-single-domain (PSD) size. Such a burnt soil layer is the main source of the ca. 50 nT amplitude magnetic field anomaly at a sensor height of 15cm observed over the excavated palaeohearth, as well as over an experimental hearth. Copyright (c) 2013 John Wiley & Sons, Ltd.