Alternatively to the usual evaluation summary, a characteristic of small cell lung cancer, is the probability of significant diffuse metastases; the prognosis is directly linked to the extent of these metastases. Moreover, the assessment of the initial extension becomes heavier and more costly as investigations continue and each new technology appears. In order to evaluate the contribution of each examination, a classification has been established as a function of the time-scale to obtain the results, of the technology involved, or whether the investigation is painful or not and any likelihood of iatrogenic side-effects. An assessment in three stages is proposed to achieve the most effective and cheapest diagnosis possible. In relation to the usual technique of assessment this sequential approach allows for a 27% reduction in the time-scale for the diagnosis of diffuse disease, 51.3% in terms of technical involvement, 46.3% in terms of pain and discomfort and 53.9% in terms of iatrogenic potential. At the same time a reduction in cost of 47.5% is observed.