Under ontological scrutiny we have identified two competing interpretations of disorder concepts in SNOMED. Should codes be interpreted as representing pathological conditions themselves or the situations in which a patient has those conditions? This difference has significant implications for the proposed harmonization between SNOMED CT and the new ICD-11 disease classification and indeed for any systematic review of the correctness of the SNOMED CT hierarchies. Conditions themselves are distinct, whereas in any given situation a patient may have more than one condition. In such cases, SNOMED codes that represent combinations of conditions - which can be regarded as "additive" - are evidence for interpreting the codes as referring to situations. There are clearly some such codes. We conducted a survey to determine the extent of this phenomenon. Three criteria were used - analysis of the SNOMED CT fully specified name, the corresponding logical definition, and the children of the concept under scrutiny. All three showed that at least 11% of concepts met our criteria for representing situations rather than conditions, with a satisfactory inter-rater reliability for the first two. We, therefore, conclude that if a uniform interpretation of SNOMED disorder codes is desired, they should be interpreted as representing situations.