Background: Antonovsky’s Sense of Coherence (SOC) scale, published with 29 items, is considered a social concept, also used in mental health research. A scale using only 13 of the items has been suggested, without explanation as to how these 13 items were selected. Aim: To compare how total scores based on 29 and 13 and the remaining 16 items could be explained by sociodemographic and mental health factors and to explore how each of the 13 items relates to these factors in comparison to the remaining 16 items. Methods: The full SOC questionnaire was completed by 1,164 subjects in the Lundby cohort study in 1997. Using linear regression, socio-demographic factors were evaluated as predictors for the sum-scores of the 29 and 13 items. Relationships to the socio-demographic factors and mental disorders were evaluated for each item; the results for the 13 items were compared to the results for the remaining 16 items. The distributions of the responses for the 13 items were compared to the distributions of the responses for the 16 items. Results: The sum-scores related differently to age; generally, positively among the 13 items, but negatively for the 16 excluded items. Differences between the 13 and the remaining 16 items were observed in relations to gender and partnership, somewhat less to socio-economic status, minor differences in relation to mental disorders. The distributions of the responses of the items were highly negatively skewed, more so among the 13 items. Conclusion: No obvious explanation for the selection of the 13 items was found. Different results may be obtained regarding associations to socio-demographic factors depending on whether the 13 items or all 29 items are used. The highly skewed distributions of responses indicate that more research would be valuable in order to assess SOC.