diff --git a/span-processing-config-service-api/src/main/proto/org/hypertrace/span/processing/config/service/v1/span_filter.proto b/span-processing-config-service-api/src/main/proto/org/hypertrace/span/processing/config/service/v1/span_filter.proto
index a7cb10df..20f3efe5 100644
--- a/span-processing-config-service-api/src/main/proto/org/hypertrace/span/processing/config/service/v1/span_filter.proto
+++ b/span-processing-config-service-api/src/main/proto/org/hypertrace/span/processing/config/service/v1/span_filter.proto
@@ -8,6 +8,7 @@ message SpanFilter {
   oneof span_filter_expression {
     LogicalSpanFilterExpression logical_span_filter = 1;
     RelationalSpanFilterExpression relational_span_filter = 2;
+    UnarySpanFilterExpression unary_span_filter = 3;
   }
 }
 
@@ -16,6 +17,14 @@ message LogicalSpanFilterExpression {
   repeated SpanFilter operands = 2;
 }
 
+message UnarySpanFilterExpression {
+  oneof left_operand {
+    string span_attribute_key = 1;
+    Field field = 2;
+  }
+  UnaryOperator operator = 3;
+}
+
 message RelationalSpanFilterExpression {
   oneof left_operand {
     string span_attribute_key = 1;
@@ -61,3 +70,9 @@ enum RelationalOperator {
   RELATIONAL_OPERATOR_REGEX_MATCH = 6;
   RELATIONAL_OPERATOR_IN = 7;
 }
+
+enum UnaryOperator {
+  UNARY_OPERATOR_UNSPECIFIED = 0;
+  UNARY_OPERATOR_EXISTS = 1;
+  UNARY_OPERATOR_NOT_EXISTS = 2;
+}